JP4919309B2 - Metal oxide platinum composite catalyst for oxygen reduction and production method thereof - Google Patents

Description

The present invention relates to a metal oxide platinum composite catalyst for oxygen reduction in which a platinum catalyst is supported on the surface of a metal oxide such as silica and a method for producing the same.

  Platinum is not only a decorative product due to its processability, heat resistance, oxidation resistance, corrosion resistance and electrochemical characteristics, but also circuit contact materials, exhaust gas purification catalysts, fuel cell electrode catalysts, gas reforming catalysts, photocatalysts, It is used for various industrial materials such as solar cells. For example, when used as a catalyst, platinum is supported in the form of particles on a support according to the purpose. In addition, since platinum is an expensive noble metal, for example, in order to increase the utilization efficiency as a catalyst, it is attempted to increase the active surface area by using it in the form of nanoparticles having a diameter of about 1 to 10 nm. A surface area is desired.

  As described above, platinum nanoparticles are used by being supported on various carriers, and the usefulness of the platinum catalyst varies greatly depending on the carrier used and the supporting method. For example, in a catalyst for a fuel cell, it is common to use carbon particles having a high current collecting ability and a large specific surface area as a carrier, and an electrode material in which nano-sized platinum is supported in a highly dispersed manner is used. . Also, in the photocatalyst, improvement in catalytic activity has been recognized by supporting platinum on titania.

  However, for example, the carbon support is oxidatively corroded due to long-term operation, battery load fluctuations, and repeated amplitude of voltage due to start and stop. In addition, platinum nanoparticles supported in a highly dispersed state increase in morphology due to repeated aggregation, resulting in a reduction in active surface area and a significant reduction in initial efficiency. Therefore, for example, nano particles of titania, alumina (refer to Patent Document 1), silica (refer to Patent Document 2) or tungsten (refer to Patent Document 3), which are corrosion-resistant metal oxides, are combined with carbon as a carrier. A method to use has been proposed.

JP2008-181696 JP 2004-363056 A JP-A-2005-174869

  However, since the material used for the carrier in the above-described conventional technique is carbon, carbon-free is not realized, and the oxide particles supported on the carbon carrier only suppress the oxidative corrosion of the carrier. . If a metal oxide support is used instead of the carbon support, the metal oxide support itself has low conductivity, so that when the platinum particles are simply dispersed on the surface, the function as a platinum catalyst is exhibited. I can't.

  The present invention has been made to solve the above-described problems, and aims to realize high catalytic activity without causing oxidative corrosion of the support.

As a result of diligent efforts by the present inventors to achieve the above object, a platinum salt is attached to silica , ceria, zirconia or titania metal oxide nanoparticles having extremely high corrosion resistance, and is generally used as a method for supporting platinum particles. By using a new spray method instead of the impregnation method that has been used in the past, we succeeded in producing a metal oxide platinum composite catalyst for oxygen reduction that does not cause oxidative corrosion of the support and has high catalytic activity. . Specifically, the present invention is as follows.

The metal oxide platinum composite catalyst for oxygen reduction according to the present invention has a scanning speed of 20 to 100 mV / sec, a scanning range of 0.01 to 1.5 V (vs. RHE), and a sulfuric acid electrolyte degassed with nitrogen gas. In the cyclic voltammogram evaluated by cyclic voltammetry after 5 to 50 cycle stabilization, the catalyst shows two peaks in the curve of anode current and cathode current between 0 and 0.4V.

The metal oxide platinum composite catalyst for oxygen reduction according to the present invention has a scanning speed of 5 mV / sec, a scanning range of 1.5 to 0.01 V (vs. RHE), and the number of revolutions in a sulfuric acid electrolyte saturated with oxygen gas. Activation dominant current value (i _k-s ) per active platinum surface area (ECSA) at 0.85 V evaluated by linear sweep voltammetry under conditions of 500 to 3000 rpm is 0.2 mA / cm ² or more It is a catalyst.

The metal oxide platinum composite catalyst for oxygen reduction according to the present invention further has an activation dominant current value ( _ik-mass ) per platinum mass of 40 A / g or more at 0.85 V evaluated by linear sweep voltammetry. It is a catalyst.

The metal oxide platinum composite catalyst for oxygen reduction according to the present invention has a rate of 0. 0 after 40 hours in an accelerated deterioration test by repeated potential scanning of 0.6 to 1.4 V in an oxygen saturated electrolytic solution at a scanning speed of 50 mV / sec. The catalyst has an activation dominant current value ( _ik-mass ) per mass of platinum at 85 V of 50% or more of the initial value.

The method for producing a metal oxide platinum composite catalyst for oxygen reduction according to the present invention comprises a metal oxide-containing material and platinum so as to contain 5 to 95 parts by weight of metal oxide and 95 to 5 parts by weight of platinum as the balance. A platinum precursor solution preparation step of preparing a platinum precursor solution by mixing salt, a spraying step of spraying the platinum precursor solution onto a substrate heated to 60 to 200 ° C., and a metal oxide from the substrate A recovery step of recovering the metal oxide platinum composite containing platinum, and firing the recovered metal oxide platinum composite in a reducing atmosphere at a temperature not lower than the temperature of the substrate during the spraying step and not higher than 300 ° C. Firing step.

The method for producing a metal oxide platinum composite catalyst for oxygen reduction according to the present invention is particularly a production method in which the metal-containing material is colloidal silica.

The method for producing a metal oxide platinum composite catalyst for oxygen reduction according to the present invention is, in particular, a production method in which a platinum salt is tetraammineplatinum chloride (II) monohydrate.

The above oxygen-reducing metal oxide platinum composite catalyst has excellent oxygen reduction activity, deterioration resistance is also very good material, compared to catalysts produced by conventional impregnation methods, inter alia, platinum High oxygen reduction activity per weight. In particular, the voltammogram of the metal oxide platinum composite catalyst for oxygen reduction obtained by cyclic voltammetry has a unique shape (a shape having two peaks) between 0 and 0.4 V (vs. RHE) for both anode and cathode currents. It is the material which shows. Further, the spraying step of the method for producing a metal oxide platinum composite catalyst for oxygen reduction according to the present invention can realize a form in which the platinum catalyst is dispersed in a state of being connected in a dendritic or thin plate shape on the surface of the metal oxide. It is possible to increase the utilization rate of the catalyst, improve the recovery rate, and reduce the process cost.

  According to the present invention, high catalytic activity can be achieved without causing oxidative corrosion of the support.

FIG. 1 illustrates a method of calculating an activation dominant current value i _k-mass (A / g) per platinum unit _mass and an activation dominant current value i _k-s (mA / cm ² ) per platinum unit surface area. It is a figure for doing. FIG. 2 is a diagram for explaining a method of calculating the active specific surface area (ECSA) of platinum from hydrogen desorption waves in cyclic voltammetry (CV). 3 is a graph showing CV evaluation results of each metal oxide platinum composite catalyst produced under the conditions of Example 1. FIG. 4 is a graph showing LSV evaluation results of each metal oxide platinum composite catalyst produced under the conditions of Example 1. FIG. FIG. 5 is a partially enlarged view of the graph shown in FIG. 6 is a graph showing CV evaluation results of each metal oxide platinum composite catalyst produced under the conditions of Example 2. FIG. FIG. 7 is a graph showing LSV evaluation results of each metal oxide platinum composite catalyst produced under the conditions of Example 2. FIG. 8 is a partially enlarged view of the graph shown in FIG. FIG. 9 is a transmission electron micrograph of a metal oxide platinum composite catalyst having a platinum loading of 50% by weight prepared under the conditions of Example 2. FIG. 10 is a transmission electron micrograph of a metal oxide platinum composite catalyst having a platinum loading of 75% by weight prepared under the conditions of Example 2. FIG. 11 is a graph showing the CV evaluation results of each metal oxide platinum composite catalyst produced under the conditions of Example 3. FIG. 12 is a graph showing LSV evaluation results of each metal oxide platinum composite catalyst produced under the conditions of Example 3. FIG. 13 is a partially enlarged view of the graph shown in FIG. FIG. 14 is a transmission electron micrograph of a metal oxide platinum composite catalyst having a platinum loading of 50% by weight produced under the conditions of Example 3. FIG. 15 is a scanning electron micrograph of a metal oxide platinum composite catalyst having a platinum loading of 50% by weight produced under the conditions of Example 3. FIG. 16 is a graph showing the CV evaluation results of each metal oxide platinum composite catalyst produced under the conditions of Example 4. FIG. 17 is a transmission electron micrograph of a metal oxide platinum composite catalyst having a platinum loading of 20% by weight prepared under the conditions of Example 4. FIG. 18 is a scanning electron micrograph of a metal oxide platinum composite catalyst with a platinum loading of 30 wt% produced under the conditions of Example 4. FIG. 19 is a graph showing the relationship between the amount of platinum supported and the active specific surface area of each metal oxide platinum composite catalyst using colloidal silica having different average particle diameters. FIG. 20 is a graph showing the relationship between platinum loading and _{ik-s of} each metal oxide platinum composite catalyst using colloidal silica having different average particle diameters. FIG. 21 is a graph showing the relationship between platinum loading and _{ik-mass of} each metal oxide platinum composite catalyst using colloidal silica with different average particle diameters. FIG. 22 is a graph showing the CV waveform of each metal oxide platinum composite catalyst produced under the conditions of Example 5. 23 is a graph showing LSV waveforms of each metal oxide platinum composite catalyst produced under the conditions of Example 5. FIG. FIG. 24 is a graph showing CV waveforms of each metal oxide platinum composite catalyst produced under the conditions of Example 6. 25 is a graph showing LSV waveforms of each metal oxide platinum composite catalyst produced under the conditions of Example 6. FIG. 26 is a graph showing CV waveforms of each metal oxide platinum composite catalyst produced under the conditions of Example 7. FIG. 27 is a graph showing LSV waveforms of each metal oxide platinum composite catalyst produced under the conditions of Example 7. FIG. 28 is a graph showing CV waveforms of each metal oxide platinum composite catalyst produced under the conditions of Example 8. FIG. 29 is a graph showing LSV waveforms of each metal oxide platinum composite catalyst produced under the conditions of Example 8. FIG. 30 is a graph showing CV waveforms of each metal oxide platinum composite catalyst produced under the conditions of Example 9. FIG. FIG. 31 is a graph showing LSV waveforms of each metal oxide platinum composite catalyst produced under the conditions of Example 9. FIG. 32 is a graph showing the relationship between the amount of platinum supported and the active specific surface area of each metal oxide platinum composite catalyst. FIG. 33 is a graph showing the relationship between the amount of platinum supported by each metal oxide platinum composite catalyst and the relationship between _ik-s . FIG. 34 is a graph showing the relationship between the amount of platinum supported and _{ik-mass of} each metal oxide platinum composite catalyst using each metal oxide platinum composite catalyst having different average particle diameters. FIG. 35 is a transmission electron micrograph of a ceria platinum composite catalyst with a platinum loading of 75% by weight produced under the conditions of Example 5. FIG. 36 is a transmission electron micrograph of a platinum oxide composite catalyst having a platinum loading of 75% by weight produced under the conditions of Example 9. FIG. 37 is a transmission electron micrograph of a zirconia platinum composite catalyst with a platinum loading of 40% by weight produced under the conditions of Example 6. FIG. 38 is a low-magnification scanning micrograph of a commercially available Pt / C catalyst. FIG. 39 is a high-magnification scanning micrograph of a commercially available Pt / C catalyst. FIG. 40 is a low-magnification scanning micrograph of a commercially available PtCo / C catalyst. FIG. 41 is a high-magnification scanning micrograph of a commercially available PtCo / C catalyst. FIG. 42 is an X-ray diffraction chart of Pt 50 wt% / PL-7, Pt 20 wt% / PL-20 and a commercially available Pt / C catalyst. FIG. 43 is a graph showing CV evaluation results before respective deterioration tests of Pt 50 wt% / PL-7, Pt 20 wt% / PL-20, a commercially available Pt / C catalyst, and a commercially available PtCo / C catalyst. FIG. 44 is a CV chart showing the results of deterioration tests of Pt 50 wt% / PL-7, Pt 20 wt% / PL-20, a commercially available Pt / C catalyst, and a PtCo / C catalyst. FIG. 45 is an LSV chart showing the results of deterioration tests of Pt 50 wt% / PL-7, Pt 20 wt% / PL-20, a commercially available Pt / C catalyst, and a PtCo / C catalyst. FIG. 46 shows the deterioration cycle time of Pt50 wt% / PL-7, Pt20 wt% / PL-20, commercially available Pt / C catalyst and PtCo / C catalyst and i _k-mass per unit mass of platinum (A / g). It is a graph which shows the relationship. FIG. 47 shows the relationship between the deterioration cycle time of Pt50 wt% / PL-7, Pt20 wt% / PL-20, commercially available Pt / C catalyst and PtCo / C catalyst and the change in ik _-mass (A / g). It is a graph to show. FIG. 48 is a graph showing the relationship between the test time and the active specific surface area (ECSA) of platinum according to Test 1 for Pt 50 wt% / PL-7, Pt 20 wt% / PL-20, commercially available Pt / C catalyst and PtCo / C catalyst. It is. FIG. 49 is a graph showing the relationship between the test time and the change rate of ECSA in Test 1 for Pt50 wt% / PL-7, Pt20 wt% / PL-20, commercially available Pt / C catalyst and PtCo / C catalyst. FIG. 50 is a CV chart showing the results of each deterioration test by Test 2 of Pt50 wt% / PL-7 and a commercially available Pt / C catalyst. FIG. 51 is an LSV chart showing the results of each deterioration test in Test 2 for Pt50 wt% / PL-7 and a commercially available Pt / C catalyst. FIG. 52 is a graph showing the relationship between the test time according to Test 2 and ik _-mass (A / g) of Pt50 wt% / PL-7 and a commercially available Pt / C catalyst. FIG. 53 is a graph showing the relationship between the test time of Pt50 wt% / PL-7 and a commercially available Pt / C catalyst according to Test 2 and the change in ik _-mass (A / g). FIG. 54 is a graph showing the relationship between ECSA and the test time according to Test 2 for Pt50 wt% / PL-7 and a commercially available Pt / C catalyst. FIG. 55 is a graph showing the relationship between the test time of Pt50 wt% / PL-7 and a commercially available Pt / C catalyst according to Test 2 and the rate of change in ECSA. FIG. 56 is a graph showing changes in ik _-mass (A / g) with time transition at various holding potentials in the deterioration test by Test 3 of Pt50 wt% / PL-7. FIG. 57 is a graph showing a change in _ik-mass (A / g) with a transition of time at various holding potentials in a deterioration test by a test 3 of a commercially available Pt / C catalyst. FIG. 58 is a CV chart showing the results of each deterioration test by Test 3 of Pt50 wt% / PL-7 and a commercially available Pt / C catalyst. FIG. 59 is an LSV chart showing the results of each deterioration test in Test 3 of Pt50 wt% / PL-7. FIG. 60 is an LSV chart in which the vicinity of the circle in the chart of FIG. 59 is enlarged. FIG. 61 is an LSV chart showing the results of each deterioration test by Test 3 of a commercially available Pt / C catalyst. FIG. 62 is an LSV chart showing an enlargement of the vicinity of the circle in the chart of FIG. FIG. 63 is a graph showing the relationship between the holding potential and ik _-mass (A / g) of Test 50 for Pt50 wt% / PL-7 and a commercially available Pt / C catalyst. FIG. 64 is a graph showing the relationship between the holding potential of Pt50 wt% / PL-7 and a commercially available Pt / C catalyst according to Test 3 and the rate of change of ik _-mass (A / g). FIG. 65 is a graph showing the relationship between holding potential and ECSA according to Test 3 for Pt 50 wt% / PL-7 and a commercially available Pt / C catalyst. FIG. 66 is a graph showing the relationship between the holding potential and the ECSA change rate in Test 3 of Pt50 wt% / PL-7 and a commercially available Pt / C catalyst. 67 is a transmission electron micrograph of each metal compound platinum composite catalyst of Example 13. FIG. 68 is a transmission electron micrograph of each metal compound platinum composite catalyst of Example 14. FIG. 69 is a transmission electron micrograph of each metal compound platinum composite catalyst of Example 15. FIG. FIG. 70 is a graph showing CV waveforms of the metal compound platinum composite catalysts of Examples 13 to 15. FIG. 71 is a graph showing LSV waveforms of the metal compound platinum composite catalysts of Examples 13 to 15. 72 is a graph showing CV waveforms of the respective metal compound platinum composite catalysts of Example 16. FIG. 73 is a graph showing LSV waveforms of each metal compound platinum composite catalyst of Example 16. FIG. 74 is a graph showing CV waveforms of the respective metal compound platinum composite catalysts of Example 17. FIG. 75 is a graph showing LSV waveforms of each metal compound platinum composite catalyst of Example 17. FIG. 76 is a graph showing CV waveforms of the respective metal compound platinum composite catalysts of Example 18. FIG. 77 is a graph showing LSV waveforms of each metal compound platinum composite catalyst of Example 18. FIG. 78 is a graph showing the CV waveform for the platinum composite catalyst of Example 19. FIG. FIG. 79 is a graph showing current values measured according to the number of rotations at the rotating electrode for the metal oxide platinum composite catalyst of Example 19. FIG. 80 is a graph showing the CV waveform for the metal oxide platinum composite catalyst of Example 20. FIG. 81 is a graph showing current values measured at the ring electrode in accordance with the voltage when the metal oxide platinum composite catalyst of Example 20 was measured at the rotating electrode. FIG. 82 is a graph showing the current value measured at the disk electrode in accordance with the voltage when the metal oxide platinum composite catalyst of Example 20 was measured at the rotating electrode. FIG. 83 is a graph showing the current value measured at the ring electrode according to the voltage with respect to the amount of platinum carried when measured with the metal oxide platinum composite catalyst rotating electrode of Comparative Example 4. . FIG. 84 is a graph showing the current value measured at the ring electrode according to the voltage with respect to the amount of platinum carried when the metal oxide platinum composite catalyst of Example 20 was measured at the rotating electrode. is there. FIG. 85 is a graph showing the CV waveform for the metal oxide platinum composite catalyst of Example 21. FIG. 86 is a graph showing current values measured at the ring electrode according to voltage when the metal oxide platinum composite catalyst of Example 21 was measured at the rotating electrode. FIG. 87 is a graph showing current values measured at the disk electrode in accordance with the voltage when the metal oxide platinum composite catalyst of Example 21 was measured at the rotating electrode. FIG. 88 is a graph showing the CV waveform for the metal oxide platinum composite catalyst of Example 22. FIG. 89 is a graph showing current values measured at the ring electrode according to voltage when the metal oxide platinum composite catalyst of Example 22 was measured at the rotating electrode. FIG. 90 is a graph showing current values measured at the disk electrode in accordance with the voltage when the metal oxide platinum composite catalyst of Example 22 was measured at the rotating electrode.

Next, each embodiment of the metal oxide platinum composite catalyst for oxygen reduction of the present invention and the production method thereof will be described. Hereinafter, unless otherwise specified, the metal oxide platinum composite catalyst for oxygen reduction is simply referred to as “metal oxide platinum composite catalyst”.

1. 1.1 Metal Oxide Platinum Composite Catalyst 1.1 Material A metal oxide platinum composite catalyst is a catalyst having a form in which platinum particles are supported on the surface of a metal oxide. The form of the metal oxide is preferably a granular material having an average particle diameter of 1 to 1000 nm. In particular, the average particle diameter is preferably in the range of 10 to 500 nm, more preferably 20 to 300 nm. As the average particle size of the metal oxide is larger, the oxygen reduction activity of the catalyst tends to be higher. Here, the “average particle diameter” of the metal oxide means an average value of particle diameters (about 500 particles) measured from an image observed with a transmission electron microscope.

The platinum is preferably a dendritic material having an active specific surface area of ^{2 to} 30 m ² / g. Here, “active specific surface area (ECSA)” of platinum means a value calculated based on FIG. 2 described later. Platinum preferably has an active specific surface area of ^{2 to} 30 m ² / g and high crystallinity. The size of the platinum crystallite is preferably 10 nm or more, more preferably 15 to 30 nm, and particularly preferably 19 to 22 nm.

  The metal oxide platinum composite catalyst can also be produced by mixing metal oxide particles and platinum particles, but is preferably a metal oxide-containing material such as a sol or gel containing a metal oxide, or a metal alkoxide. And a compound containing platinum (for example, a platinum salt), and then dried and fired.

  The weight of platinum in the metal oxide platinum composite catalyst is in the range of 5 to 95 wt%, and is preferably as small as possible from the viewpoint of manufacturing cost. However, since the amount of platinum supported is also required to have high oxygen reduction activity as a catalyst and to form a network by contacting platinum with each other, the amount of platinum supported is as small as possible while satisfying these requirements. Is preferred. In order to form a network by bringing platinum into contact with each other, it is preferable to realize a form in which platinum is dispersed in a state of being connected in a needle shape, a net shape, a tree shape, or a thin plate shape. Further, the larger the average particle size of the metal oxide, the higher the oxygen reduction activity as a catalyst, even if the amount of platinum supported is small.

1.2 Oxygen reduction activity ability The oxygen reduction reaction is a reaction represented by O ₂ + 4H ₃ O ⁺ + 4e ⁻ → 6H ₂ O, and it is considered that an activation overvoltage is caused by the slow reaction. Therefore, the activation overvoltage is reduced by using an electrode material that is excellent in activity for oxygen reduction reaction. In this embodiment, a potentiostat, a rotating disk electrode, and a three-electrode cell are used, and the measurement temperature is set to a predetermined temperature within a range of 40 to 70 ° C. (for example, 60 ° C.). The oxygen reduction activity of the composite catalyst is examined by measuring cyclic voltammetry (CV) and linear sweep voltammetry (LSV). In addition, it is preferable to use a catalyst-supporting glassy carbon, a standard hydrogen electrode, and a platinum mesh for the working electrode, the reference electrode, and the counter electrode, respectively.

  The measurement conditions for CV are, for example, a scanning speed of 20 to 100 mV / sec, a scanning range of 0.01 to 1.5 V (vs. RHE), and 5 to 50 cycles after stabilization in a sulfuric acid electrolyte degassed with nitrogen gas. Is preferable. The measurement conditions for LSV are, for example, a scanning speed of 3 to 8 mV / sec, a scanning range of 1.5 to 0.01 V (vs. RHE), a sulfuric acid electrolyte saturated with oxygen gas, and a rotational speed of 200 to 5000 rpm. It is preferable to measure 3 to 10 points at a predetermined number of revolutions within the range. In addition, you may use the electrolyte solution which uses not only a sulfuric acid electrolyte solution but another acid (hydrochloric acid etc.).

  A suitable metal oxide platinum composite catalyst according to this embodiment has a scanning speed of 20 to 100 mV / sec, a scanning range of 0.01 to 1.5 V (vs. RHE), and a sulfuric acid electrolyte degassed with nitrogen gas. In the cyclic voltammogram evaluated by CV after 5 to 50 cycle stabilization, two peaks are shown in the curve of anode current and cathode current between 0 to 0.4V.

The oxygen reduction activity of the metal oxide platinum composite catalyst is determined by the method shown in FIG. 1, the activation dominant current value i _k-mass (A / g) per platinum unit _mass and the activation dominant current per platinum unit surface area. The value i _k-s (mA / cm ² ) is calculated. A specific calculation method is as follows.

First, a current value (i) obtained under a plurality of rotation speed conditions in LSV measurement (voltage: 0.85 V) is obtained. Next, the rotational speed (converted from the rotational speed) into the ω ^1/2 -i ^-1 coordinate system with ω ^1/2 on the horizontal axis (X axis) and i ⁻¹ on the vertical axis (Y axis). Plot the reciprocal coordinates of the value of ½ of ω, unit: rad / sec and the current value (i, unit: A), and draw the most approximate line (Koutecky-Levic plot). As a result, an expression of 1 / i = 1 / i _k + 1 / 0.620 · n · F · A · C · D ^2/3 · v ^1/6 · ω ^1/2 can be created. Here, n: number of reaction electrons, F: Faraday constant 9.65 × 10 ⁴ (C / mol), A: electrode surface area (cm ² ), C: activity (mol / cm ³ ), D: diffusion coefficient (Cm ² / sec), v: kinematic viscosity (cm ² / sec) of the solution, and ω: rotational speed (rad / sec).

Next, ik is _obtained from the value of the Y-axis intercept by extrapolating the straight line specified by the above equation. The _{i k} is the amount of platinum supported activated governing current values of platinum per unit mass divided by _{(g) i k-mass (} A / g). Also active specific surface area of the platinum _{i k} activation governing current values of platinum per unit surface area divided by _{^{(cm 2 / g) i k}} -s (mA / cm 2). The larger i _k-mass (A / g) and i _k-s (mA / cm ² ), the higher the oxygen reduction activity ability of the catalyst.

A suitable metal oxide platinum composite catalyst according to this embodiment is rotated in a sulfuric acid electrolyte saturated with oxygen gas at a scanning speed of 5 mV / sec, a scanning range of 1.5 to 0.01 V (vs. RHE). The activation dominant current value per platinum surface area at 0.85 V evaluated by LSV under the condition of several 500 to 3000 rpm is 0.2 mA / cm ² or more. A more preferable metal oxide platinum composite catalyst has an activation dominant current value per platinum mass of 40 A / g or more at 0.85 V evaluated by LSV under the same conditions as described above.

  Moreover, it is preferable to evaluate a metal oxide platinum catalyst by the following several deterioration tests (accelerated deterioration test) supposing start and stop. One is scanning speed: 20 to 100 mV / sec, atmosphere: sulfuric acid electrolyte saturated with oxygen gas, scanning range: 0.6 to 1.4 V (vs. RHE), 10 to 100 hours in repeated potential scanning. In this method, the CV and LSV are evaluated later under the above conditions to evaluate deterioration. In addition, with respect to the catalyst material, in a sulfuric acid electrolyte saturated with oxygen gas, the test electrode is at an arbitrary potential given from the range of 1.2 to 1.8 V (vs. RHE), in the range of 0.5 to 3 hours. There is a method of evaluating the deterioration (stability) by evaluating the LSV and the CV after holding for a predetermined time. In order to confirm the potential stability of the catalyst material, for example, the holding potential is preferably evaluated at several points such as 1.3 V, 1.4 V, and 1.5 V.

  A suitable metal oxide platinum composite catalyst according to this embodiment has a scanning speed of 50 mV / sec, 40 hours in a repetitive potential scan in an oxygen saturated electrolyte solution with a scan range of 0.6 to 1.4 V (vs. RHE). The activation dominant current value per platinum mass at a later 0.85 V is 50% or more of the initial value.

2. 2. Method for Producing Metal Oxide Platinum Composite Catalyst 2.1 Platinum Precursor Solution Preparation Step A platinum salt, a metal-containing material, and at least one of water and an organic solvent are mixed until uniform to obtain a platinum precursor solution. Make it. In mixing, it is preferable to perform a diffusion treatment using ultrasonic waves. The platinum salt and the metal-containing material may be appropriately changed so that the weight ratio of platinum in the composite catalyst is 5 to 95 wt%, more preferably 10 to 50 wt%. it can. As the platinum salt, hexachloroplatinic acid, dinitrodiammine platinum, dinitrodiammine platinum nitrate, dinitrodiaquaplatinum, tetraammineplatinum chloride, chloroplatinic acid, tetraammineplatinum (II) chloride monohydrate, hexaammineplatinum chloride are used. In particular, tetraammineplatinum (II) chloride monohydrate can be suitably used. In this embodiment, each metal oxide is dispersed by hand ultrasonic waves in at least one of distilled water and an organic solvent or a mixed solution thereof, and there is at least one of distilled water and an organic solvent or a mixture thereof. A platinum precursor solution ultrasonically dispersed in the mixed solution was added.

As the metal of the metal oxide, Li, Al, Si, P, B, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ru, Pb, Ag, Cd, In, Sn, Sb, W, Ce, etc. can be mentioned. Examples of oxide _{M x O z, A x M} y O z, Mx (DO 4) y, A x M y (DO 4) z (M: metal element, A: an alkali metal or a lanthanoid element, D: Be, B, Si, P, Ge, etc.), and these solid solutions can also be used. For example, silica, titania, zirconia, ceria and tin oxide can be suitably used as the metal oxide. As silica, colloidal silica can be particularly preferably used. As titania, zirconia, ceria and tin oxide, a dispersion of fine particles can be particularly preferably used.

  As the organic solvent, alcohols such as methanol, ethanol, propanol, isopropanol, and butanol, or ketones such as acetone can be used. Of these, isopropanol can be preferably used. In the case of mixing distilled water and an organic solvent and using silica as the metal oxide, it is preferable that the ratio of distilled water: organic solvent is 5: 5 or that the organic solvent is increased. In addition, when zirconia or ceria is used as the metal oxide, the ratio of distilled water: organic solvent is preferably about 4: 6.

2.2 Spraying process The platinum precursor solution prepared in the above process is put in a spray container and sprayed onto a substrate heated to 60 to 200 ° C., preferably 80 to 120 ° C. An oxide platinum composite can be obtained. The platinum precursor solution is solidified on the substrate to become a metal oxide platinum composite. The heating temperature of the substrate may be outside the above temperature range as long as the temperature is sufficient to solidify the platinum precursor solution. For example, the platinum precursor solution obtained in the platinum precursor solution preparation step may be sprayed onto a portion having a surface temperature of 105 ° C. by hand spraying.

2.3 Recovery Step Next, after cooling the substrate to room temperature, the metal oxide platinum composite deposited on the substrate or not deposited on the substrate is recovered. When peeling the deposit from the substrate, a silicone resin spatula can be preferably used.

2.4 Firing Step Next, the recovered metal oxide platinum composite is heated at a temperature higher than the temperature of the substrate during the spraying step and not higher than 300 ° C. in a reducing atmosphere. As the reducing gas, a mixed gas of nitrogen and hydrogen can be used. Preferably, a hydrogen / nitrogen mixed gas containing 10% by volume of hydrogen is used. The heating temperature during the firing step may be outside the above temperature range as long as the metal oxide platinum composite catalyst has catalytic ability. As the firing temperature, it is preferable to select a temperature at which platinum has a high degree of crystallinity and can maintain a fine particle form. In this example, the obtained powder was calcined at 200 ° C. for 2 hours in an atmosphere of 10% hydrogen and 90% nitrogen.

1. Method for producing metal oxide platinum composite catalyst The metal oxide platinum composite catalyst was produced under the following conditions.

1.1 Raw Material Tetraammineplatinum chloride (II) monohydrate manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. was used as a platinum salt as a raw material for platinum. Colloidal silica (product numbers: PL-1, PL-3, PL-7 and PL-20) manufactured by Fuso Chemical Co., Ltd. was used as the silica-containing material as the metal oxide. PL-1 is colloidal silica having an average particle diameter: 15 nm, specific gravity: 1.07, and silica content: 12% by weight. PL-3 is colloidal silica having an average particle size: 35 nm, specific gravity: 1.12, and silica content: 20% by weight. PL-7 is colloidal silica having an average particle size: 75 nm, specific gravity: 1.14, and silica content: 23% by weight. PL-20 is colloidal silica having an average particle size: 220 nm, specific gravity: 1.12, and silica content: 20% by weight. The ceria (cerium oxide, CeO ₂ ) material as a metal oxide includes a ceria dispersion aqueous solution (product number: BYK-3810, average particle size: 10 nm, specific gravity: 1.21, content of ceria manufactured by Big Chemie Japan Co., Ltd. : 17.5 wt%). As the zirconia (zirconium oxide, ZrO ₂ ) as the metal oxide, a zirconia dispersed aqueous solution (average particle size: 100 nm or less, zirconia content: 10 wt%) manufactured by Sigma-Aldrich Japan Co., Ltd. was used. Titania (titanium oxide, TiO ₂ ) as a metal oxide includes titania-dispersed aqueous solution (product number: STS-02, average particle size: 7 nm, titania content: 35.56 wt%) manufactured by Ishihara Sangyo Co., Ltd. A titania-dispersed aqueous solution (product number: 643017, average particle size: 75 nm or less, titania content: 35 wt%) manufactured by Japan Co., Ltd. was used. Tin oxide (SnO ₂ ) as a metal oxide is a tin oxide dispersed aqueous solution (product number: TDL-S, particle diameter 50 to 85 nm, specific gravity 1.16, tin oxide content 18 wt%) manufactured by Mitsubishi Materials Corporation. Using.

  As the alcohol, ethanol (Ethanol: EtOH) manufactured by Wako Pure Chemical Industries, Ltd. was used. A product manufactured by Wako Pure Chemical Industries, Ltd. was used for isopropanol (IPA). A product manufactured by Wako Pure Chemical Industries, Ltd. was used as isobutanol (IBA).

1.2 Platinum precursor solution preparation process 0.232 g of tetraammineplatinum (II) chloride monohydrate, 0.0258-0.928 g of metal oxide, 2.5 ml of distilled water and 2.5 ml of EtOH as alcohol Sonic diffusion treatment was performed to prepare a platinum precursor solution. In addition, when PL-20 was used for colloidal silica and Pt was 10% by weight, the amount of EtOH added was 0.37 ml, and the amount of distilled water added was 0.13 ml.

1.3 Spraying Step The platinum precursor solution was sprayed onto a glass substrate in a state heated to 100 ° C. in a spray container (Korani HA2400) manufactured by Harder & Stenbeck.

1.4 Recovery Step Next, after cooling the substrate to room temperature, the metal oxide platinum composite was recovered from the substrate.

1.5 Firing Step Next, the recovered metal oxide platinum composite was heated to 200 ° C. in a 10% hydrogen / nitrogen atmosphere. The heating time was 2 hours.

2. Evaluation Method The oxygen reduction activity of the metal oxide platinum composite catalyst was evaluated by performing two electrochemical measurements, cyclic voltammetry (referred to as “CV”) and linear sweep voltammetry (referred to as “LSV”). In addition, an accelerated deterioration test was performed assuming start and stop. For these electrochemical measurements, a potentiostat (model: HSV100) and rotating disk electrode control system manufactured by Hokuto Denko Co., Ltd. and a triode cell manufactured by Nitto Keiki Co., Ltd. were used. The measurement temperature was 60 ° C., and 0.5 M sulfuric acid (pH: 0.38) was used as the electrolyte. The pH of the electrolytic solution was adjusted by diluting sulfuric acid manufactured by Wako Pure Chemical Industries, Ltd. with distilled water. As the working electrode and the reference electrode, 10 μg catalyst-supported glassy carbon (φ5 mm, 19.625 mm ² ) and a standard hydrogen electrode manufactured by Micro Corporation were used, respectively. Further, Pt mesh (100 mesh, 20 × 30 mm) manufactured by Niraco Co., Ltd. was used for the counter electrode.

  The working electrode was produced by the following method. Polishing cylindrical glassy carbon (bottom diameter: 5 mm) using # 2000 and # 3000 Emily paper (manufactured by Nihon Kenshi Co., Ltd.) in turn, followed by alumina polishing with an average particle size of 1 μm and 0.05 μm Using the agents in order, buffing was performed for 5 minutes to finish the mirror surface. A polishing machine KENT3 manufactured by Engis was used for buffing, and a polishing paper manufactured by Buehler was used for the water-resistant polishing paper. After mirror polishing, put glassy carbon in distilled water and perform ultrasonic cleaning for 2 minutes, then perform ultrasonic cleaning in ethanol for 2 minutes, and finally put in distilled water and perform ultrasonic cleaning for 2 minutes. went. Then, it dried at 80 degreeC for 1 hour, and stored in the desiccator.

  Next, 1 ml of Nafion ionomer (Aldrich 5 wt% alcohol water mixed solution) and 300 ml of ethanol are sufficiently mixed by ultrasonic treatment for 10 minutes, and 10 μl is supplied to the bottom surface of the glassy carbon taken out from the desiccator, Dried at 25 ° C. for 1 hour. On the other hand, 10 mg of the sintered metal oxide platinum composite and 10 ml of ethanol water mixed solvent (a solvent in which ethanol and distilled water are mixed at a weight ratio of 9: 1) are subjected to ultrasonic dispersion for 30 minutes. 10 μl was taken out and supplied to the bottom surface of the glassy carbon after the drying. Then, it dried at 25 degreeC for 1 hour, and also dried at 80 degreeC for 1 hour, and was set as the electrode for a test.

  CV evaluation conditions were: scanning speed: 50 mV / sec, scanning range: 0.02 to 1.2 V (vs. RHE), atmosphere: sulfuric acid electrolyte degassed with nitrogen gas (hereinafter referred to as “nitrogen saturated atmosphere” And evaluated after 20 cycles stabilization. The LSV is a scanning speed: 5 mV / sec, a scanning range: 1.05 to 0.05 V (vs. RHE), an atmosphere: a sulfuric acid electrolyte saturated with oxygen gas (hereinafter referred to as “oxygen saturated atmosphere” as appropriate). ) And the number of revolutions: 500, 1000, 1500, 2000, 2500, 3000 rpm, and 6 conditions, respectively.

For the accelerated deterioration test, the following three methods were adopted.
Test 1: Assuming start-stop, scanning speed: 50 mV / sec, atmosphere: oxygen-saturated electrolyte, scanning range: 0.8 to 1.3 V (vs. RHE), 20 hours and 40 hours later, the CV , LSV was evaluated to evaluate deterioration.

  Test 2: Assuming start and stop, scanning speed: 50 mV / sec, atmosphere: in oxygen-saturated electrolyte, scanning range: 0.9 to 1.3 V (vs. RHE), 20 hours, 40 hours and 60 hours later The above CV and LSV were evaluated to evaluate deterioration.

  Test 3: In an oxygen-saturated electrolyte, after holding for 1 hour at three constant potentials of 1.3 V, 1.4 V, and 1.5 V, the above LSV and CV were evaluated and deteriorated. Evaluated. The CV evaluation was performed after 20 cycles stabilization, and the other conditions were the same as the CV evaluation conditions.

  For the crystal structure analysis, an X-ray diffractometer (model: RINT2500HF) manufactured by Rigaku Corporation was used. The measurement conditions were CuKα line, scanning speed: 2 degrees / min, and step width: 0.02 degrees. For observation of the fine structure, a transmission electron microscope (model: JEM2010) manufactured by JEOL Ltd. and a scanning electron microscope (model: S-5000) manufactured by Hitachi, Ltd. were used.

The platinum active specific surface area (ECSA) was calculated from the hydrogen desorption wave in CV. Specifically, the area (integrated value) of the hatched portion shown in FIG. 1 is the charge amount Q _H (μC) required for desorption of the monomolecular adsorption layer of hydrogen, and the charge amount of adsorbed hydrogen per unit area of platinum is 210 ( μC / cm ² ) was determined from platinum active specific surface area = Q _H / (210 × platinum supported amount).

Quantitative evaluation on the generation of hydrogen peroxide of the metal oxide platinum composite catalyst was performed using a rotating ring disk electrode (RRDE). The value of the current flowing when hydrogen peroxide generated from the catalyst at the time of LSV measurement after CV measurement was supplemented by the surrounding platinum ring electrode (width 1 mm, interval 0.5 mm from the disk electrode) was recorded as needed. A predetermined amount of the catalyst to be evaluated was supported on a glassy carbon disk (φ6 mm, 28.26 mm ² ) as a working electrode. For these electrochemical measurements, EcoChemie B. et al. V. A dual potentiostat (model: AUTOLAB) manufactured by the company, a rotating disk electrode control system manufactured by Hokuto Denko Corporation, and a triode cell manufactured by Nitto Keiki Co., Ltd. were used. The measurement temperature was 60 ° C., and 0.1 M perchloric acid aqueous solution was used as the electrolyte. The concentration of the electrolytic solution was adjusted by diluting perchloric acid (for precision analysis) manufactured by Wako Pure Chemical Industries, Ltd. with distilled water. A micro standard hydrogen electrode was used as the reference electrode. Further, Pt mesh (100 mesh, 20 × 30 mm) manufactured by Niraco Co., Ltd. was used for the counter electrode.

  In the CV for evaluating the generation of hydrogen peroxide of the metal oxide platinum composite catalyst, the scanning speed is 50 mV / sec, the scanning range is 0.02 to 1.2 V (vs. RHE), and the atmosphere is degassed with nitrogen gas. The perchloric acid electrolyte (hereinafter referred to as “nitrogen-saturated atmosphere” as appropriate) was evaluated after 20 cycles of stabilization. In addition, LSV is a scanning speed: 5 mV / sec, scanning range: 1.05-0.05 V (vs. RHE), atmosphere: perchloric acid electrolyte saturated with oxygen gas (hereinafter referred to as “oxygen saturated atmosphere” And the rotation speed was 2000 rpm. At this time, the potential of the ring electrode was adjusted to 1.0 V (vs. RHE), and the numerical value of the current flowing by the reaction on this electrode was recorded.

3. Production conditions and evaluation results 3.1 Oxygen reduction activity test "Example 1"
Using colloidal silica, PL-1 having an average particle size of 15 nm, a metal oxide platinum composite catalyst was prepared so that the supported amount of platinum was 35, 43, 75, and 90% by weight.

  Table 1 shows the characteristics of the metal oxide platinum composite catalyst. FIG. 3 shows the evaluation results of CV. 4 and 5 show a graph of the LSV evaluation results and a partially enlarged view thereof, respectively.

As shown in Table 1, it was found that the platinum active specific surface area and _ik-mass increase as the amount of platinum supported increases. Moreover, _ik-s was 0.2 mA / cm ² or more except for the case where the platinum loading was 35 wt%. Further, as shown in FIG. 3, regardless of the amount of platinum supported, the anode and cathode currents both show a unique shape having two peaks between 0 and 0.3 V (vs. RHE). The shape became remarkable with the increase of. Thus, having two large peaks means that there are two main potentials at which hydrogen is desorbed, and the surface area of platinum is large. Since the hydrogen desorption energy differs depending on the crystal plane of platinum, it is considered that the metal oxide platinum composite catalyst produced in this example was mainly supported by platinum having two crystal planes and a large surface area. . Further, as shown in FIGS. 4 and 5, it was found that the oxygen reduction starting potential shifts to the high potential side with an increase in the amount of platinum supported. From these results, it was found that when PL-1 was used for colloidal silica, the oxygen reduction activity was maximized at a platinum loading of 90% by weight.

"Example 2"
A metal oxide platinum composite catalyst was prepared by using PL-3 having an average particle diameter of 35 nm on colloidal silica so that the platinum loading was 50, 70, 75 and 80 wt%.

  Table 2 shows the characteristics of the metal oxide platinum composite catalyst. FIG. 6 shows CV evaluation results. 7 and 8 show a graph of LSV evaluation results and a partially enlarged view thereof, respectively.

As shown in Table 2, it was found that the platinum active specific surface area and _ik-mass were maximized when the supported amount of platinum was 75% by weight. The maximum value exceeded 40 A / g. Moreover, i _k-s was 0.2 mA / cm ² or more in all of the platinum loading of 50 to 80 wt%. Furthermore, as shown in FIG. 6, regardless of the amount of platinum supported, the anode and cathode currents both show a unique shape having two peaks between 0 and 0.3 V (vs. RHE). Was 75% by weight, and the shape became most prominent. Further, as shown in FIGS. 7 and 8, when the platinum loading is 75% by weight, the oxygen reduction start potential shifts to the highest potential side, and when it reaches 80% by weight, the oxygen reduction start potential may be lowered. all right. From these results, it was found that when PL-3 was used as colloidal silica, the oxygen reduction activity was maximized at a platinum loading of 75% by weight.

  9 and 10 are transmission electron micrographs of the respective metal oxide platinum composite catalysts having platinum loadings of 50 wt% and 75 wt%, respectively.

  All the metal oxide platinum composite catalysts were found to be in a state where platinum and silica were mixed at the nano level.

"Example 3"
A metal oxide platinum composite catalyst was prepared by using PL-7 with colloidal silica having an average particle diameter of 75 nm so that the supported amount of platinum was 40, 50, 62.5, and 75% by weight.

  Table 3 shows the characteristics of the metal oxide platinum composite catalyst. FIG. 11 shows CV evaluation results. 12 and 13 show a graph of LSV evaluation results and a partially enlarged view thereof, respectively.

As shown in Table 3, it was found that the platinum active specific surface area and _ik-mass were maximized when the supported amount of platinum was 50% by weight. The maximum value exceeded 40 A / g. Moreover, i _k-s was 0.2 mA / cm ² or more in all of the platinum loading of 40 to 75 wt%. Furthermore, as shown in FIG. 11, regardless of the amount of platinum supported, the anode and cathode currents both show a unique shape having two peaks between 0 and 0.3 V (vs. RHE). Was 50% by weight, and the shape became most prominent. Furthermore, as shown in FIGS. 12 and 13, when the amount of platinum supported is 50% by weight, the oxygen reduction start potential shifts to the highest potential side, and when it reaches 62.5% by weight, the oxygen reduction start potential decreases. I understood it. From these results, it was found that when PL-7 was used as colloidal silica, the oxygen reduction activity was maximized at a platinum loading of 50% by weight.

  14 and 15 are a transmission electron micrograph and a scanning electron micrograph of a metal oxide platinum composite catalyst having a platinum loading of 50% by weight, respectively.

  As shown in FIGS. 14 and 15, the metal oxide platinum composite catalyst using colloidal silica (PL-7) having an average particle diameter of 75 nm has a form in which platinum nanoparticles are entangled in a dendritic manner on the surface of the silica particles. I found out.

Example 4
A metal oxide platinum composite catalyst was prepared using PL-20 with colloidal silica having an average particle diameter of 220 nm so that the supported amount of platinum was 10, 20, 30, 40 and 50% by weight.

  Table 4 shows the characteristics of the metal oxide platinum composite catalyst. FIG. 16 shows CV evaluation results. FIGS. 17 and 18 are a transmission electron micrograph of a metal oxide platinum composite catalyst having a platinum loading amount of 20% by weight and a scanning electron micrograph of a metal oxide platinum composite catalyst having a platinum load of 30% by weight, respectively. .

As shown in Table 4, it was found that the platinum active specific surface area and _ik-mass were maximized when the supported amount of platinum was 10% by weight. The i _k-mass exceeded 40 A / g except in the case of a platinum loading of 50 wt%. Moreover, i _k-s was 0.2 mA / cm ² or more in all of platinum loadings of 10 to 50 wt%. Furthermore, as shown in FIG. 16, when the amount of platinum supported was 10% by weight or more, both the anode and cathode currents showed a unique shape having two peaks between 0 and 0.3 V (vs. RHE). . However, at a platinum loading of 10% by weight, three peaks sometimes appeared and were slightly unstable. As shown in FIGS. 17 and 18, the metal oxide platinum composite catalyst using colloidal silica (PL-20) having an average particle size of 220 nm has platinum nanoparticles on the surface of the silica particles as in Example 3. It was found to have a tangled form. As a result of SEM and TEM observations, the other metal oxide platinum composite catalysts in the respective examples also had a form in which platinum particles were entangled in a dendritic manner on the silica particle surface.

"Summary of Examples 1-4"
Platinum content of each metal oxide platinum composite catalyst using different colloidal silica of average particle diameter, the relationship between the activity ratio platinum mass i _k-mass and activity ratio platinum surface area i _k-s, respectively 19, 20 and It shows in FIG.

  It was found that when the average particle size of silica in the colloidal silica increases, the peak of oxygen reduction activity tends to shift to a lower platinum loading amount and the absolute value tends to increase. From this result, it was found that the amount of platinum added can be reduced by using silica having a relatively large average particle diameter.

"Examples 5 to 9"
In Examples 5 to 9, each metal oxide in Table 5 was used as a support. Specifically, in Example 5, measurement was performed for each sample using ceria as a carrier and platinum loadings of 30, 40, 50, 75, and 90 wt%. In Example 6, measurement was performed on each sample using zirconia as a carrier and platinum loadings of 30, 40, 50, and 75 wt%. It was. In Example 7, the measurement was performed for each sample with titania supported by Ishihara Sangyo Co., Ltd. and platinum loadings of 50, 75, and 90 wt%. In Example 8, measurement was performed on each sample with platinum loadings of 50 wt% and 75 wt% using Sigma Aldrich Japan Co., Ltd. titania as a carrier. In Example 9, measurement was performed on each sample using tin oxide as a carrier and having platinum loadings of 50 wt% and 75 wt%.

  In Table 6, the characteristic of each metal oxide platinum composite catalyst of Examples 5-9 is shown. Moreover, the waveform of CV obtained about Examples 5-9 is shown to FIG.22,24,26,28,30, respectively. The LSV waveforms obtained for Examples 5 to 9 are shown in FIGS. 23, 25, 27, 29, and 31, respectively.

"Summary of Examples 5-9"
As shown in the CV waveforms of FIGS. 22, 24, 26, 28, and 30, when a metal oxide other than silica is used as the support, the anode and cathode currents are both 0 to 0.3 V (vs. RHE). It showed a unique shape with two peaks. Further, the activation dominant current value i _k-mass per platinum supported amount of each metal oxide platinum composite catalyst using each metal oxide as a carrier and the activation dominant current value i _k-s per active specific surface area The relationships are shown in FIGS. 32, 33 and 34, respectively.

  As shown in Table 6, when ceria and zirconia are used as the carrier, the oxygen reduction activity tends to decrease as the proportion of platinum carried increases, and the activity is reduced at a platinum amount of less than 50% by mass ratio. It was found that there was a peak. In addition, when titania manufactured by Sigma-Aldrich Japan Co., Ltd. was used as a carrier, the platinum active specific surface area did not tend to increase regardless of the ratio of platinum. On the other hand, when titania manufactured by Ishihara Sangyo Co., Ltd. was used as the carrier, it was confirmed that the activity was improved by supporting 50 wt% or more of platinum. Tin oxide is a conductive metal oxide, but even when it was used as a support, the oxygen reducing ability of platinum could be confirmed. From these results, it was found that a material using a metal oxide having no electrical conductivity other than silica (ceria, titania, zirconia) as a carrier is also a catalyst capable of expressing the oxygen reduction activity of platinum.

  FIGS. 35 to 37 are transmission electron micrographs of a ceria platinum composite catalyst having a platinum loading of 75% by weight, a tin oxide platinum secondary catalyst having a platinum loading of 75%, and a zirconia platinum composite catalyst having a platinum loading of 40%, respectively. .

  All metal oxide platinum composite catalysts were found to be in a state where platinum and metal oxide were mixed at the nano level. When the carrier was ceria, platinum covering the carrier in a dendritic manner was relatively linear. Further, when the carrier is zirconia, the platinum branch-like portions covering the carrier in a dendritic manner are stretched more like a mesh.

3.2 Accelerated degradation test of oxygen reduction activity “Example 10”
Metal oxide platinum composite catalyst (Pt50 wt% / PL-7) with 50 wt% platinum support using PL-7 as colloidal silica and 20 wt% platinum support using PL-20 as colloidal silica. % Of the metal oxide platinum composite catalyst (Pt20 wt% / PL-20) was evaluated for deterioration in oxygen reduction activity. The evaluation was performed using Test 1 out of the three test methods described above.

“Comparative Example 1”
As a comparison with the metal oxide platinum composite catalyst that was evaluated in Example 10, a commercially available Pt / C catalyst (made by Tanaka Kikinzoku Kogyo Co., Ltd., TEC10E50E, Pt46.4 wt%) in which platinum particles are supported on carbon particles and A commercially available PtCo / C catalyst (manufactured by Tanaka Kikinzoku Co., Ltd., TEC36E52, Pt 46.5 wt%, Co 4.7 wt%) in which platinum particles and cobalt particles are supported on carbon particles was used.

  FIGS. 38 and 39 are low and high magnification scanning micrographs of a commercially available Pt / C catalyst, respectively. 40 and 41 are scanning micrographs of a commercially available PtCo / C catalyst at low and high magnification, respectively.

  As is apparent from the above scanning micrograph, the commercially available Pt / C catalyst and PtCo / C catalyst both have a form in which platinum fine particles are individually dispersed and supported on carbon particles. Examples 1-4 As in the case of the metal oxide platinum composite catalyst, platinum particles are not in a dendritic form on the support surface.

  FIG. 42 is an X-ray diffraction chart of Pt 50 wt% / PL-3, Pt 50 wt% / PL-7, Pt 50 wt% / PL-20, Pt 20 wt% / PL-20 and a commercially available Pt / C catalyst.

  From the comparison of the X-ray diffraction images shown in FIG. 42, it was found that the metal oxide platinum composite catalyst supported platinum having extremely high crystallinity as compared with a commercially available catalyst. Further, from the half width of the peak (around 2θ = 39 °) on the Pt (111) plane, the Scherrer equation “D = Kλ / βcos θ, D: crystallite diameter, K: 0.94, λ: wavelength of X-ray (here Then, the crystallite diameter (nm) was calculated using “1.54056 angstrom) and β = half-value width (rad) −0.14 × π / 180 (rad)”. As a result, the crystallite diameter of Pt50wt% / PL-3 = 19.1nm, the crystallite diameter of Pt50wt% / PL-7 = 21.3nm, the crystallite diameter of Pt50wt% / PL-20 = 21.6nm, Pt20wt% / PL-20 crystallite size = 21.9 nm and commercially available Pt / C catalyst crystallite size = 2.5 nm.

  Table 7 shows the characteristics of the metal oxide platinum composite catalyst and the commercially available catalyst. FIG. 43 shows the evaluation results of CV before the deterioration test.

As shown in Table 7, the Pt 50 wt% / PL-7 and Pt 20 wt% / PL-20 metal oxide platinum composite catalysts were compared with the commercially available catalysts in the active specific surface area of platinum and the activation per unit mass of platinum. Although i _k-mass (A / g), which is the dominant current value, is small, i _k-s (mA / cm ² ), which is the activation dominant current value per unit surface area of platinum, is large, 0.2 mA / cm ^2. It was over. Further, when comparing the CV before the deterioration test, the metal oxide platinum composite catalyst of Pt 50 wt% / PL-7 and Pt 20 wt% / PL-20 has both anode and cathode currents of 0 to 0.3 V (vs. RHE). ) Showed a peculiar shape with two peaks, but no shape having two distinct peaks was found in the commercially available catalyst. These two peaks are hydrogen desorption peaks.

  FIG. 44 is a CV chart showing the results of each deterioration test according to Test 1 for Pt50 wt% / PL-7, Pt20 wt% / PL-20, a commercially available Pt / C catalyst, and a PtCo / C catalyst. FIG. 45 is an LSV chart showing the results of each deterioration test according to Test 1 for Pt50 wt% / PL-7, Pt20 wt% / PL-20, a commercially available Pt / C catalyst, and a PtCo / C catalyst.

  As shown in FIG. 44, Pt 50 wt% / PL-7 (A) and Pt 20 wt% / PL-20 (B) were tested compared to commercially available Pt / C catalyst (C) and PtCo / C catalyst (D). The change in the hydrogen adsorption / desorption peak with respect to time was small. Further, as shown in FIG. 45, Pt 50 wt% / PL-7 (A) and Pt 20 wt% / PL-20 (B) are compared with commercially available Pt / C catalyst (C) and PtCo / C catalyst (D). The shift of the oxygen reduction starting potential to the low potential side (left side of FIG. 45) with respect to the test time was small. From these results, it is considered that Pt50 wt% / PL-7 and Pt20 wt% / PL-20 are excellent catalysts compared to commercially available Pt / C catalysts and PtCo / C catalysts.

Tables 8 to 11 show changes in various characteristics according to the transition of the test time according to Test 1 of Pt50 wt% / PL-7, Pt20 wt% / PL-20, commercially available Pt / C catalyst and PtCo / C catalyst, respectively. . FIG. 46 and FIG. 47 show the test time and ik _-mass (A / P) for Pt 50 wt% / PL-7, Pt 20 wt% / PL-20, commercially available Pt / C catalyst and PtCo / C catalyst, respectively. It is a graph which shows the relationship between g) and a test time, and the change of _ik-mass (A / g). 48 and 49 show the test time and the active specific surface area (referred to as ECSA) according to Test 1 of Pt 50 wt% / PL-7, Pt 20 wt% / PL-20, commercially available Pt / C catalyst and PtCo / C catalyst, respectively. It is a graph which shows the relationship between a relationship and test time, and the change rate of ECSA.

  As shown in Tables 8 to 11 and FIGS. 46 and 47, the commercially available Pt / C catalyst and PtCo / C catalyst showed a significant decrease in oxygen reduction activity as the test time increased, whereas Pt 50 wt% / PL It can be seen that −7, Pt20 wt% / PL-20 has a small decrease in oxygen reduction activity, maintains 50% or more of the initial value, and is excellent in durability. In addition, as shown in Tables 6 to 9, FIG. 48 and FIG. 49, the commercially available Pt / C catalyst and PtCo / C catalyst greatly decrease the active specific surface area of platinum as the test time increases. Pt50 wt% / PL-7 and Pt20 wt% / PL-20 are considered to have a small decrease in active specific surface area and do not change greatly in form. Even after the accelerated deterioration test shown in Test 1 above, Pt50 wt% / PL-7 and Pt20 wt% / PL-20 have a small change in active specific surface area (ECSA) and recover the performance of platinum (potential scanning, etc.) Therefore, it is considered that the oxygen reduction activity can be recovered to a value close to the initial value. On the other hand, the commercially available Pt / C catalyst and PtCo / C catalyst have a large change in the particle size of platinum particles, and even when treatment for recovering the performance of platinum is performed, the initial oxygen reduction activity cannot be recovered. Conceivable.

"Example 11"
Degradation of oxygen reduction activity of a metal oxide platinum composite catalyst (Pt 50 wt% / PL-7) having a platinum loading of 50 wt% using PL-7 as colloidal silica was evaluated. The evaluation was performed using Test 2 out of the three test methods described above.

"Comparative Example 2"
As a comparison with the metal oxide platinum composite catalyst as an evaluation target of Example 11, a commercially available Pt / C catalyst (made by Tanaka Kikinzoku Kogyo Co., Ltd., TEC10E50E, Pt46.4 wt%) in which platinum particles are supported on carbon particles is used. Using.

  FIG. 50 is a CV chart showing the results of each deterioration test by Test 2 of Pt50 wt% / PL-7 and a commercially available Pt / C catalyst. FIG. 51 is an LSV chart showing the results of the respective deterioration tests by Test 2 of Pt50 wt% / PL-7 and a commercially available Pt / C catalyst.

  As shown in FIG. 50, the change in the shape of the hydrogen adsorption / desorption peak with respect to the test time was small in Pt 50 wt% / PL-7 (A) compared to the commercially available Pt / C catalyst (B). In addition, as shown in FIG. 51, Pt50 wt% / PL-7 (A) is lower than the commercially available Pt / C catalyst (B) on the lower potential side of the oxygen reduction start potential with respect to the test time (left side of FIG. 51). The shift to was small. From this result, it is considered that Pt50 wt% / PL-7 is a catalyst having a small change in the shape of platinum particles and excellent in durability as compared with a commercially available Pt / C catalyst.

Tables 12 and 13 show changes in various characteristics according to the transition of the test time according to Test 2 of Pt50 wt% / PL-7 and a commercially available Pt / C catalyst, respectively. FIG. 52 and FIG. 53 show the relationship between the test time by test 2 and i _k-mass (A / g) of Pt 50 wt% / PL-7 and a commercially available Pt / C catalyst, and the test time and i _{k−, respectively.} It is a graph which shows the relationship with the change of _mass (A / g). FIGS. 54 and 55 are graphs showing the relationship between the test time and ECSA, and the relationship between the test time and the ECSA change rate, respectively, according to Test 2 for Pt50 wt% / PL-7 and a commercially available Pt / C catalyst.

  As shown in Table 12, Table 13, FIG. 52, and FIG. 53, the commercially available Pt / C catalyst greatly decreases the oxygen reduction activity as the test time becomes longer, whereas Pt 50 wt% / PL-7 It can be seen that the decrease in oxygen reduction activity is small, maintaining 60% or more of the initial value, and excellent in durability. Further, as shown in Table 12, Table 13, FIG. 54, and FIG. 55, the commercially available Pt / C catalyst has a Pt 50 wt% / PL while the active specific surface area of platinum greatly decreases as the test time increases. -7 is considered that the decrease in active specific surface area is small and the form does not change greatly. Even after the accelerated deterioration test shown in Test 2 above, Pt50 wt% / PL-7 has a small change in the active specific surface area (ECSA), and the oxygen reduction activity of the Pt50 wt% / PL-7 is reduced by treatment (potential scanning, etc.) that restores the platinum performance It is considered possible to recover to a value close to the initial value. On the other hand, the commercially available Pt / C catalyst has a large change in the particle size of the platinum particles by the accelerated deterioration test, and it is considered that the initial oxygen reduction activity cannot be recovered even when the treatment for recovering the performance of platinum is performed. It is done.

"Example 12"
In the same manner as in Example 11, the deterioration of the oxygen reduction activity of a platinum oxide composite catalyst (Pt50 wt% / PL-7) having a platinum loading of 50 wt% using PL-7 as colloidal silica was evaluated. Evaluation was performed using Test 3 out of the three test methods described above.

“Comparative Example 3”
As a comparison with the metal oxide platinum composite catalyst used as the evaluation target of Example 12, as in Comparative Example 2, a commercially available Pt / C catalyst in which platinum particles are supported on carbon particles (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., TEC10E50E, Pt 46.4 wt%) was used.

FIG. 56 and FIG. 57 show changes in ik _-mass (A / g) depending on the transition of time at various holding potentials in the deterioration test by Test 3 of Pt50 wt% / PL-7 and a commercially available Pt / C catalyst, respectively. It is a graph which shows.

As is clear from comparison between FIG. 56 and FIG. 57, at all holding potentials of 1.3 V, 1.4 V, and 1.5 V, Pt50 wt% / PL-7 is compared to the commercially available Pt / C catalyst. The change in i _k-mass (A / g) was small. In addition, with the commercially available Pt / C catalyst, the flowing current increased as the holding potential increased. From this, in the case of a commercially available Pt / C catalyst, the flowing current value is considered to include the corrosion current of the carbon support.

  FIG. 58 is a CV chart showing the results of each deterioration test by Test 3 of Pt50 wt% / PL-7 and a commercially available Pt / C catalyst. FIG. 59 and FIG. 60 are an LSV chart showing a result of each deterioration test by the test 3 of Pt50 wt% / PL-7 and a partial enlarged chart thereof. 61 and 62 are an LSV chart showing a result of each deterioration test by Test 3 of a commercially available Pt / C catalyst and a partial enlarged chart thereof.

  As shown in FIG. 58, Pt 50 wt% / PL-7 (A) had a smaller change in the hydrogen adsorption / desorption peak after holding the constant potential than the initial Pt / C catalyst (B). In addition, as shown in FIGS. 59 to 62, Pt50 wt% / PL-7 had a smaller degree of shift of the oxygen reduction starting potential to the lower potential side after holding 1.5 V, as compared with the commercially available Pt / C catalyst. . From this result, it is considered that Pt50 wt% / PL-7 is a catalyst having a small change in the shape of platinum particles and excellent in durability as compared with a commercially available Pt / C catalyst.

Tables 14 and 15 show changes in various characteristics after holding a constant potential according to Test 3 of Pt50 wt% / PL-7 and a commercially available Pt / C catalyst, respectively. FIG. 63 and FIG. 64 show the relationship between the holding potential and i _k-mass (A / g) of Pt50 wt% / PL-7 and a commercially available Pt / C catalyst according to Test 3, and the holding potential and i _{k−, respectively.} It is a graph which shows the relationship with the change rate of _mass (A / g). FIG. 65 and FIG. 66 are graphs showing the relationship between the holding potential and ECSA and the relationship between the holding potential and the ECSA change rate according to Test 3 of Pt50 wt% / PL-7 and a commercially available Pt / C catalyst, respectively.

  As shown in Table 14, Table 15, FIG. 63, and FIG. 64, the commercially available Pt / C catalyst has a significant decrease in oxygen reduction activity as the holding potential increases compared to Pt 50 wt% / PL-7. Thus, it can be seen that Pt50 wt% / PL-7 has a small decrease in oxygen reduction activity, maintains 80% or more of the initial value even at a holding potential of 1.5 V, and is excellent in durability. Moreover, as shown in Table 14, Table 15, FIG. 65, and FIG. 66, the commercially available Pt / C catalyst has a Pt 50 wt% / PL while the active specific surface area of platinum greatly decreases as the holding potential increases. In -7, the decrease in the active specific surface area was small. From this, it is considered that Pt50 wt% / PL-7 does not greatly change the form of platinum even when the holding potential is increased. Even after the above overload test, Pt 50 wt% / PL-7 has a small change in the active specific surface area (ECSA), and the oxygen reduction activity is close to the initial value by the treatment for recovering the performance of platinum (such as potential scanning). It is considered possible to recover to the value. On the other hand, the commercially available Pt / C catalyst has a large change in the particle size of the platinum particles due to the overload test, and it is considered that the initial oxygen reduction activity cannot be recovered even when treatment for recovering the performance of platinum is performed. It is done.

4). Examination and Evaluation Results of Dispersion Solvent of Metal Oxide Platinum Catalyst “Examples 13 to 15”
In Examples 13 to 15, as shown in Table 9, EtOH, IPA and IBA were used as the types of alcohols contained in the solvent added when preparing the platinum precursor solution or dispersing the metal oxide, respectively. The oxygen activity of the produced catalyst was evaluated. The solvent was mainly composed of alcohol and water, and the amount of alcohol was the same as that of water. Further, silica (PL-7) was used as the carrier. In Table 16, the characteristic of each metal oxide platinum composite catalyst of Examples 13-15 is shown. In addition, transmission electron micrographs of the silica platinum composite catalysts of Examples 13 to 15 are shown in FIGS. The CV waveforms of the metal compound platinum composite catalysts of Examples 13 to 15 are shown in FIG. Moreover, the LSV waveform of each metal compound platinum composite catalyst of Examples 13-15 is shown in FIG.

"Examples 16 to 18"
As shown in the catalytic activity specific platinum surface area _ik-s in Table 16, the oxygen reduction activity of the metal compound platinum composite catalyst when IPA was used as the solvent was the highest.

  Next, IPA was used as a solvent to be added when preparing the platinum precursor solution or dispersing the metal oxide, and the mixing ratio of the IPA and water was examined. As shown in Table 17, in Example 16, silica (PL-7) was used as a carrier. In Example 17, ceria was used as a carrier. In Example 18, zirconia was used as the carrier. 72, 74, and 76 show the CV waveforms of the metal oxide platinum composite catalysts of Examples 16 to 18, respectively. 73, 75, and 77 show the LSV waveforms of the metal oxide platinum composite catalysts of Examples 16 to 18, respectively.

As shown in Table 17, it was found that even when the platinum loading was the same, the oxygen reduction activity was different depending on the solvent composition. Comparing the _ik-mass of Example 16, when silica was used as the support, when IPA more than the same amount as H ₂ O was used, the oxygen reduction activity was excellent. Further, from Example 17, when ceria was used as the carrier, no influence on the oxygen reduction activity by H ₂ O and IPA with different mixing ratios was observed. Furthermore, from Example 18, when zirconia was used as the carrier, the highest oxygen reduction activity was exhibited when more IPA than H ₂ O was added.

"Summary of Examples 13-18"
From Examples 13-15, it turned out that the oxygen reduction activity of a metal compound platinum composite catalyst changes with kinds of alcohol used as a solvent. In particular, the oxygen reduction activity of the metal compound platinum composite catalyst when IPA was used as the solvent was the highest. Moreover, from Examples 16-18, it turned out that the ratio of alcohol and water used as a solvent which shows the highest oxygen reduction activity is determined by the kind of each support | carrier. In particular, when silica PL-7 and zirconia were used as carriers, the higher the amount of IPA relative to water, the higher the oxygen reduction activity.

5. Examination and Evaluation of Drying Method “Example 19”
In Example 19, the platinum precursor solution obtained in the platinum precursor solution preparation step is not sprayed onto the portion having a surface temperature of 105 ° C. by hand spraying, but a spray dryer (model: SD-1) having a set temperature of 105 ° C. , Manufactured by Tokyo Rika Kikai Co., Ltd.) to produce a metal oxide platinum composite catalyst. Silica (PL-7) was used as the carrier. FIG. 78 shows the CV waveform for the platinum composite catalyst of Example 19. In FIG. 79, the electric current value measured according to rotation speed with the rotating electrode about the metal oxide platinum composite catalyst of Example 19 is shown. Table 18 shows the characteristics of Example 19 obtained from CV in FIG.

When the results of Table 17 and the results of Example 16 were compared, there was no change in _ik-mass using either a spray dryer or a hand spray. Therefore, even when a spray dryer was used, a metal oxide platinum composite catalyst having the same level of activity as when hand spray was used could be produced.

6). Evaluation of H ₂ O ₂ Production Amount For example, in fuel cells, it has been confirmed that hydrogen peroxide (H ₂ O ₂ ) is generated as a byproduct during oxygen reduction. Due to the generation of H ₂ O ₂ , there is a problem that an electrolyte membrane (such as a perfluorosulfonic acid membrane) is corroded or broken. In order to reduce the maintenance cost or improve the life of the apparatus, there is a need for a platinum catalyst that can reduce the amount of H ₂ O _{2 that} causes corrosion or destruction of peripheral members. Therefore, hereinafter, the amount of H ₂ O ₂ produced was evaluated.

"Example 20"
In Example 20, the ratio of IPA and H _{2 O} as a solvent to be added upon dispersing the prepared or metal oxide of a platinum precursor solution _IPA: H 2 O = _7: 3 of metal oxide platinum composite catalyst Produced. The catalyst weight to be evaluated was changed to 0.5 μg, 1 μg, 2.5 μg, 5 μg, 10 μg, 15 μg and 25 μg, and the production of H ₂ O ₂ was evaluated by RRDE. The CV waveform for the metal oxide platinum composite catalyst of Example 20 is shown in FIG. FIG. 81 shows the results of measuring the current value detected by the ring electrode in accordance with the evaluated catalyst weight when LSV measurement was performed with the rotating electrode using the catalyst of Example 20. FIG. 82 shows the results of measuring the current value detected at the disk electrode according to the evaluated catalyst weight when LSV measurement was performed with the rotating electrode using the catalyst of Example 20. Note that the amount of H ₂ O ₂ generated tends to increase as it goes upward in the vertical axis direction of FIG.

[Comparative Example 4]
In Comparative Example 4, as a comparison with the metal oxide platinum composite catalyst of Example 20, a commercially available Pt / C catalyst having platinum particles supported on carbon particles (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., TEC10E50E, Pt 46.4 wt%) Was used. FIG. 83 shows the result of measuring the current value detected by the ring electrode when LSV measurement was performed by the rotating electrode using the catalyst of Comparative Example 4. The horizontal axis represents the amount of platinum supported, and the vertical axis represents the current value detected by the ring electrode. 84 is a graph similar to FIG. 83 measured for the catalyst of Example 20. FIG.

In FIG. 84, when the potential of the rotating disk electrode is 0.6 V or more, the amount of H ₂ O ₂ generated is 4 minutes compared to a commercially available catalyst in which platinum is supported on carbon as a carrier. It was 1. Therefore, the metal oxide platinum composite catalyst of Example 20 was less preferable than the catalyst of Comparative Example 4, and the amount of H ₂ O ₂ generated was small.

"Example 21"
Next, in Example 21, similarly to Example 19, a metal oxide platinum composite catalyst dried using a spray dryer was produced. Silica (PL-7) was used as the carrier. The catalyst weight to be evaluated was changed to 1 μg, 2.5 μg, 5 μg, and 10 μg, and the generation of H ₂ O ₂ was evaluated by RRDE. The CV waveform for the metal oxide platinum composite catalyst of Example 21 is shown in FIG. FIG. 86 shows the results of measuring the current value detected by the ring electrode according to the evaluated catalyst weight when LSV measurement was performed with the rotating electrode using the catalyst of Example 21. FIG. 87 shows the results of measuring the current value detected by the disk electrode according to the evaluated catalyst weight when LSV measurement was performed with the rotating electrode using the catalyst of Example 20.

"Example 22"
When comparing FIGS. 85 to 87 and FIGS. 80 to 82, the same metal oxide platinum composite catalyst as that in the case of using hand spray was able to be produced with respect to the production amount of H ₂ O ₂ and using a spray dryer. .

In Example 22, in Example 19, zirconia was used as a carrier. The catalyst weight to be evaluated was changed to 1 μg, 2 μg, 4 μg, 5 μg and 10 μg, and the production of H ₂ O ₂ was evaluated by RRDE. 88 shows the CV waveform of Example 22, and FIG. 89 shows the current value detected by the ring electrode when LSV measurement was performed with the rotating electrode using the catalyst of Example 22, according to the evaluated catalyst weight. The measurement results are shown. FIG. 90 shows the results of measuring the current value detected at the disk electrode according to the evaluated catalyst weight when LSV measurement was performed with the rotating electrode using the catalyst of Example 22.

From FIG. 89, even when zirconia was used as the carrier, the metal oxide platinum composite catalyst was preferable because the amount of H ₂ O ₂ generated was small.

  The present invention is applicable to, for example, a catalyst.

Claims (8)

5 to 95 parts by weight of a metal oxide of silica, ceria, zirconia or titania ;
95-5 parts by weight of platinum as the balance,
Including
The platinum particles have a form in which they are connected and entangled on the surface of the metal oxide particles ,
2. A metal oxide platinum composite catalyst for oxygen reduction, wherein the platinum particles have a crystallite diameter of 10 nm or more. Evaluated by cyclic voltammetry after stabilization for 5 to 50 cycles in a sulfuric acid electrolyte deaerated with nitrogen gas at a scanning speed of 20 to 100 mV / sec, a scanning range of 0.01 to 1.5 V (vs. RHE). 2. The metal oxide platinum composite catalyst for oxygen reduction according to claim 1, wherein the cyclic voltammogram shows two peaks in a curve of an anode current and a cathode current between 0 to 0.4 V. 3. Evaluation was performed by linear sweep voltammetry under conditions of a scanning speed of 5 mV / sec, a scanning range of 1.5 to 0.01 V (vs. RHE), and a sulfuric acid electrolyte saturated with oxygen gas at a rotational speed of 500 to 3000 rpm. 3. The metal oxide platinum composite catalyst for oxygen reduction according to claim 1, wherein the activation dominant current value per platinum surface area at 85 V is 0.2 mA / cm ² or more. The metal oxide platinum composite catalyst for oxygen reduction according to claim 3, wherein an activation dominant current value per platinum mass at 0.85 V evaluated by the linear sweep voltammetry is 40 A / g or more. In an accelerated deterioration test with a scanning speed of 50 mV / sec and an oxygen-saturated electrolyte in a repetitive potential scan of 0.6 to 1.4 V, the activation dominant current value per platinum mass at 0.85 V after 40 hours is the initial value. The metal oxide platinum composite catalyst for oxygen reduction according to any one of claims 1 to 4, wherein the value is 50% or more of the value. A method for producing a metal oxide platinum composite catalyst for oxygen reduction according to any one of claims 1 to 5,
A platinum precursor solution preparation step of preparing a platinum precursor solution by mixing a metal-containing material and a platinum salt so as to include 5 to 95 parts by weight of metal oxide and 95 to 5 parts by weight of platinum as a balance; ,
A spraying step of spraying the platinum precursor solution onto a substrate heated to 60 to 200 ° C .;
A recovery step of recovering a metal oxide platinum composite containing the metal oxide and the platinum from the substrate;
A firing step of firing the recovered metal oxide platinum composite in a reducing atmosphere at a temperature of not less than 300 ° C. and not less than the temperature of the substrate during the spraying step;
A method for producing a metal oxide platinum composite catalyst for oxygen reduction , comprising: The method for producing a metal oxide platinum composite catalyst for oxygen reduction according to claim 6, wherein the metal-containing material is colloidal silica. The method for producing a metal oxide platinum composite catalyst for oxygen reduction according to claim 6 or 7, wherein the platinum salt is tetraammineplatinum (II) chloride monohydrate.