CN1111083C - A kind of preparation method of anti-carbon monoxide poisoning platinum ruthenium electrocatalyst - Google Patents

Abstract

The invention relates to a preparation method of an anti-carbon monoxide _poisoning platinum ruthenium electrocatalyst. First, chloroplatinate is converted into Pt sulfite, and the Pt sulfite aqueous solution reacts with _H2O2 to produce a Pt colloidal solution; RuCl _3. The aqueous solution is added to the above Pt colloidal solution under acidic conditions to form a Pt and Ru mixed colloidal solution; the ultrasonically treated carbon carrier is added to the above mixed colloidal solution, and the Pt-Ru/C catalyst is obtained after treatment. The catalyst prepared by the invention is used as an electrode catalyst of a proton exchange membrane fuel cell and still has high catalytic activity when the CO content is as high as 100ppm.

Description

A kind of preparation method of anti-carbon monoxide poisoning platinum ruthenium electrocatalyst

technical field

The invention relates to a preparation method of an anti-carbon monoxide poisoning platinum ruthenium electrocatalyst, which belongs to the technical field of electrocatalysis.

Background technique

A fuel cell is a device that directly converts chemical energy into electrical energy. It has high energy conversion efficiency because it is not limited by the Carnot cycle. Among them, the proton exchange membrane fuel cell (PEMFC) uses _H2 and _O2 or air as the reaction medium, and the main reaction product is water, which is an ideal environment-friendly energy conversion technology. In addition, PEMFC has a low working temperature (50-125°C), and is expected to be applied in electric vehicles and small mobile power stations. It is a hot spot for high-tech research and development at home and abroad.

At present, in terms of electric vehicles, there have been prototypes at home and abroad, but they all use pure hydrogen as raw material. Since the current large-scale production of hydrogen is mainly realized through the reforming reaction of oil and natural gas and the incomplete combustion reaction and shift reaction of coal, more or less CO is contained in industrial hydrogen. The adsorption of CO on Pt is stronger than that of _H2 , and it is easy to form a strong adsorption on platinum sites, which reduces the adsorption sites of _H2 , thereby reducing the performance of the battery. Studies have shown that the ppm level of CO can lead to a sharp decline in the activity of metal Pt catalysts. However, if pure hydrogen is used as a raw material, it will undoubtedly increase the operating cost of the stack and limit the promotion of this technology. One of the solutions is to improve the Pt catalyst to improve the carbon monoxide resistance of the Pt catalyst. Existing patents and journal literatures have carried out many researches on this, and the results show that Ru is one of the better catalyst-promoting components, but at the same time, it is found that the preparation method has a great influence on the catalyst-promoting ability of Ru.

The preparation methods of Pt-Ru/C catalysts mentioned in the literature mainly include the following: (1) impregnation method. Deposit H ₂ PtCl ₆ and RuCl ₃ sequentially on the carrier XC-72R, after drying, reduce at 523K under H ₂ atmosphere to prepare Pt-Ru/C catalyst (see J.Phy.Chem., B 103(1999 ) 97-103.); (2) chemical reduction method. Such as Japanese patent JP98-334925 and JP 99-11305 disclose the method that uses formaldehyde as reducing _agent to prepare Pt-Ru/C catalyst; Preparation of Pt-Ru/C catalyst; (3) colloid method. Watanabe proposed this method to prepare Pt-Ru/C catalyst earlier. They first added NaHSO ₃ to the H ₂ PtCl ₆ solution, fully reacted to convert platinum to its sulfite, controlled the pH of the solution, and added H ₂ dropwise O ₂ solution and RuCl ₃ solution, after H ₂ O ₂ oxidizes platinum and ruthenium, then add carrier XC-72R, after boiling, filter, wash, and dry to obtain Pt-Ru/C catalyst (see J.Electronal . Chem. 229 (1987) 395-406). Later, someone improved this method, that is, Pt and Ru were first prepared into sulfite, and hydrogen peroxide solution was added to convert Pt and Ru into colloid at the same time, and the carrier XC-72R was added at the same time _. The Pt-Ru/C catalyst was obtained after reduction under atmosphere (see J. Catal., 154 (1995) 98-106). But the catalyst they prepared is mainly used for the electrooxidation of methanol. Recently, Japanese Patent JP 11-47595 used a similar method to prepare Pt-Ru/C catalysts and used them in hydrogen-oxygen proton exchange membrane fuel cells. In the above method, since the reaction of NaHSO ₃ and H ₂ PtCl ₆ and sulfite and H ₂ O ₂ should be ensured to be complete, the amount of NaHSO ₃ and H ₂ O ₂ exceeds the stoichiometric number. Therefore, there is a redox reaction of NaHSO ₃ and H ₂ O ₂ , that is, when H ₂ O ₂ is added dropwise, H ₂ O ₂ reacts with platinum sulfite and sodium bisulfite respectively at the same time, so that the formation of Pt colloids reacts Complicated, the reaction process is not suitable for control, especially when the amount of catalyst prepared is relatively large.

Contents of the invention

The object of the present invention is to propose a kind of anti-carbon monoxide poisoning platinum ruthenium electrocatalyst preparation method, this method makes the platinum-ruthenium/carbon catalyst that makes have better anti-CO poisoning ability by improving the colloid method preparation method.

The preparation method of the anti-carbon monoxide poisoning platinum ruthenium electrocatalyst proposed by the present invention comprises the following steps:

1. Preparation of platinum sulfite intermediate: Suspend chloroplatinate in deionized water to make the concentration 0.1-10g/100ml, add NaHSO ₃ saturated solution to react, so that the color of the solution gradually fades from yellow to colorless Transparent, then continue to add NaHSO ₃ until precipitation occurs, make the pH value 3-4, stir, add Na ₂ CO ₃ , make the pH value greater than 6.5, let stand, filter, wash, and dry at 90-120°C to obtain Platinum sulfite intermediate;

2. Make carbon into deionized water suspension at a concentration of 1-10g/100ml, and ultrasonically treat it for 0.5-3 hours; make the platinum sulfite intermediate prepared above into deionized water with a concentration of 0.1-10g/100ml Suspension, add sulfuric acid dropwise to make it dissolve, use NaOH to adjust the pH value = 3, in the platinum sulfite intermediate, dropwise add H ₂ O ₂ with a concentration of 30% by weight to carry out precipitation reaction, and the dropping ratio is per gram Add 30-100ml H ₂ O ₂ to the platinum sulfite intermediate, then add RuCl ₃ solution dropwise to make the pH value 15;

3. Finally, add the carbon treated in the second step above, adjust the pH value to 3-6, stir for 0.5-5 hours, heat and boil for 1-5 hours, cool, filter, wash, and dry at 90-120°C to obtain Pt -Ru/C catalyst.

The catalyst prepared by the method of the present invention is used as an electrode catalyst for a proton exchange membrane fuel cell, and still has high catalytic activity when the CO content is as high as 100ppm

Description of drawings

Fig. 1 is the Pt/C and Pt-Ru/C catalyst battery performance test result prepared by embodiment 1 and comparative example 1-2;

Fig. 2 is the Pt-Ru/C catalyst battery performance test result prepared by embodiment 1-4;

Fig. 3 is the catalyst Pt4f XPS spectrogram that embodiment 1 prepares.

Detailed ways

Embodiments of the present invention are described below.

XC-72 is used as the carbon support in the following examples, but the present invention is not limited to this carbon support.

The performance evaluation of Pt-Ru/C catalyst cell was carried out in a self-made small single cell test system. Electrode preparation is the same as the usual method, that is, the Pt-Ru/C catalyst is first mixed with an appropriate amount of 5% Nafion solution and other additives to form a viscous paste, and then evenly coated on the carbon paper. The dried carbon paper was cut into a circle with a size of 1 cm ² and hot-pressed together with a proton exchange membrane (Nafion-115) to form a three-in-one electrode assembly. The electrode was assembled into a single-cell test system, and the battery performance of the catalyst was evaluated by recording the voltammetry curve.

The battery test conditions are: electrode temperature 70°C, anode hydrogen and cathode oxygen pressures both 0.2MPa, gas humidification temperature 90°C, electrode theoretical Pt loading 0.8mg/cm ² . The concentration of CO in hydrogen is 100ppm.

Example 1:

Suspend 10g K ₂ PtCl ₆ in deionized water (concentration 1g/100ml water), add NaHSO ₃ saturated solution to react, make the solution color gradually lighten from yellow to colorless and transparent, then continue to add NaHSO ₃ until precipitation occurs, make the pH to 3.5, stir. Add Na ₂ CO ₃ to make the pH 6.6, let it stand still, filter, wash, and dry at 105°C to obtain 13.4 g of platinum sulfite intermediate.

0.2 g of carbon was made into a suspension in deionized water at a concentration of 2 g/100 ml, treated ultrasonically for 1 hour, and set aside.

Weigh 0.134g of the above-prepared sulfite intermediate (containing about 0.04g of Pt) into a 100ml beaker, add 30ml of deionized water, add H ₂ SO ₄ dropwise, adjust the pH to 3 with NaOH after dissolving, add 8ml of H ₂ dropwise O ₂ and maintain pH=3. Then 20ml of RuCl ₃ solution (containing 0.02g of Ru) was added dropwise to maintain pH=3. Add the treated carbon carrier XC-72, adjust pH=5, stir for 30 minutes, then boil for 3 hours, filter, wash, and dry overnight at 105°C after cooling to prepare a 20wt%Pt-10wt%Ru/C catalyst (with carbon as the benchmark), and the performance test results of single cells are shown in Figure 1.

Example 2

Suspend 3gK ₂ PtCl ₆ in deionized water (concentration 3g/100ml water), add NaHSO ₃ saturated solution for reaction, make the solution color gradually lighten from yellow to colorless and transparent, then continue to add NaHSO ₃ until precipitation occurs, and make the pH to 3.6, stir. Add Na ₂ CO ₃ to make the pH to 7, let stand, filter, wash, and dry at 120°C to obtain 3.99 g of platinum sulfite intermediate.

0.2g of carbon was made into a deionized water suspension at a concentration of 8g/100ml, ultrasonically treated for 0.5 hours, and set aside.

Weigh 0.134g of the above-prepared sulfite intermediate (containing about 0.04g of Pt), add 100ml of deionized water, add H ₂ SO ₄ dropwise, adjust the pH to 3 with NaOH after dissolving, add 10ml of H ₂ O ₂ dropwise and maintain pH=3. Then 20ml of RuCl ₃ solution (containing 0.02g of Ru) was added dropwise to maintain pH=5. Add the treated carbon carrier XC-72, adjust the pH=5, stir, then boil for 1 hour, filter, wash, and dry overnight at 120°C after cooling to prepare a 20wt%Pt-10wt%Ru/C catalyst (using carbon as Benchmark), the performance test results of a single battery are shown in Figure 2.

Example 3

Suspend 5gK ₂ PtCl ₆ in deionized water (concentration 6g/100ml water), add NaHSO ₃ saturated solution for reaction, make the solution color gradually lighten from yellow to colorless and transparent, then continue to add NaHSO ₃ until precipitation occurs, make the pH For 3.3, stir. Add Na ₂ CO ₃ to make the pH 7.5, let it stand still, filter, wash, and dry at 100°C to obtain 6.4 g of platinum sulfite intermediate.

0.3g of carbon was made into a suspension in deionized water at a concentration of 2g/100ml, treated ultrasonically for 2 hours, and set aside.

Weigh 0.192g of the sulfite intermediate prepared above (containing about 0.06g of Pt), add 30ml of deionized water, add H ₂ SO ₄ dropwise, adjust the pH to 3 with NaOH after dissolving, add 16ml of _{H 2} O ₂ dropwise and maintain pH=3. Then 30ml of RuCl ₃ solution (containing 0.03g of Ru) was added dropwise to maintain pH=1.5. Add the treated carbon carrier XC-72, adjust the pH=3, stir, then boil for 2 hours, filter, wash, and dry overnight at 105°C after cooling to prepare a 20wt%Pt-10wt%Ru/C catalyst (using carbon as Benchmark), the performance test results of a single battery are shown in Figure 3.

Example 4

Weigh 5.49 g of commercial carbon carrier XC-72 (purchased from Cabot Corporation, USA), add 100 ml of deionized water, and perform ultrasonic treatment for 0.5 hours, and set aside.

Weigh 3.68g of the sulfite intermediate prepared in the above example (containing about 1.098g of Pt), add 700ml of deionized water, add H ₂ SO ₄ dropwise, adjust the pH to 3 with NaOH after dissolving, and add 217ml of H ₂ O ₂ dropwise And maintain pH=3. Then 75ml of RuCl ₃ solution (containing 0.549g of Ru) was added dropwise to maintain pH=3. Add the treated carbon carrier XC-72, adjust the pH=5, stir, then boil for 3 hours, filter, wash, and dry overnight at 105°C after cooling to prepare a 20wt%Pt-10wt%Ru/C catalyst (using carbon as Benchmark), the performance test results of single battery are shown in Figure 4.

Comparative example 1

A 20wt% Pt/C catalyst was prepared using the method disclosed in CN00106170.4 (2000).

Comparative example 2

Weigh 0.3 g of commercial carbon carrier XC-72 (purchased from Cabot Corporation, USA), add 15 ml of deionized water, and perform ultrasonic treatment for 0.5 hour, and set aside. Measure 26.9ml of H ₂ PtCl ₆ aqueous solution (containing about 0.06g of Pt), add 30ml of deionized water and 0.8384g of NaHSO ₃ , stir, and add 12ml of H ₂ O ₂ dropwise after the solution is clear to maintain pH=3. Then the pH was adjusted to 7, and 20 ml of RuCl ₃ solution (containing 0.03 g of Ru) was added dropwise to maintain the pH at 7.0-7.5. Add the treated carbon carrier XC-72, adjust the pH=5, stir, then boil for 3 hours, filter, wash, and dry overnight at 105°C after cooling to prepare a 20wt%Pt-10wt%Ru/C catalyst (using carbon as Benchmark), the performance test results of a single battery are shown in Figure 1.

Claims (1)

1, a kind of preparation method of anti-carbon monoxide poisoning platinum-ruthenium electro-catalyst is characterized in that this method comprises following each step:

(1) preparation of platinum sulphite intermediate: chloroplatinate is suspended in to make its concentration in the deionized water be 0.1-10g/100ml, adds NaHSO ₃Saturated solution reacts, and makes solution colour thin out gradually until water white transparency by Huang, continues to add NaHSO then ₃Until precipitation occurring, make the pH value be 3-4, stir, add Na ₂CO ₃, make the pH value greater than 6.5, leave standstill, after filtration, washing, 90-120 ℃ obtain platinum sulphite intermediate after the oven dry down;

(2) carbon is made into deionized water suspension, ultrasonic processing 0.5-3 hour with the concentration of 1-10g/100ml;

(3) the platinum sulphite intermediate with above-mentioned preparation is made into the deionized water suspension that concentration is 0.1-10g/100ml, drips sulfuric acid and makes it dissolving, and with NaOH adjust pH=3, the dropping weight percent concentration is 30% H in this platinum sulphite intermediate ₂O ₂Carry out precipitation reaction, the dropping ratio is to add 30-100mlH in every gram platinum sulphite intermediate ₂O ₂, drip RuCl then ₃Solution makes the pH value be 1-5;

(4) add the carbon of handling through above-mentioned second step at last, adjust pH is 3-6, stirred 0.5-5 hour, and ebuillition of heated 1-5 hour, cooling, after filtration, washing, 90-120 ℃ oven dry, must the Pt-Ru/C catalyst.

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