CN113604839B - Method for preparing metal oxide passivated nickel/nickel oxide in-situ electrode - Google Patents

Abstract

The invention provides a preparation method of a metal oxide passivated nickel/nickel oxide in-situ electrode. Preparing a precursor solution containing nickel/chromium (molybdenum) ions and oxides or hydroxides of nickel/chromium (molybdenum), attaching the precursor solution to the surface of foam Nickel (NF), and applying a reduction potential in a specific electrolyte for reduction by using an electrochemical reduction method to partially reduce nickel oxide or nickel hydroxide in the precursor substance attached to the surface of the foam Nickel (NF) into metallic nickel to obtain a chromium oxide (molybdenum oxide) passivated nickel/nickel oxide in-situ electrode. The technical scheme of the invention has the advantages of low cost of the required raw materials, simple operation, short time consumption, less environmental pollution and the like; the prepared chromium oxide (molybdenum oxide) passivated nickel/nickel oxide in-situ electrode shows excellent catalytic activity as a bifunctional electrocatalyst for Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction (OER), and has good prospect of being applied to electrocatalytic decomposition of water.

Description

Preparation method of metal oxide passivated nickel/nickel oxide in situ electrode

technical field

The invention relates to the preparation of multi-component multifunctional materials, and the application belongs to the field of electrocatalysis and energy conversion materials and devices.

Background technique

Hydrogen production by electrolysis of water has the advantages of abundant raw materials and high product purity, and is considered to be one of the clean and green hydrogen production methods. However, the high energy barriers of the two half-reactions, the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), which make up the water electrolysis reaction, limit and affect the energy conversion efficiency of the electrolysis process and the development of hydrogen production technology from water electrolysis, so it is necessary to develop Highly active catalyst to lower the reaction energy barrier. So far, the most efficient electrocatalysts are still noble metal-based catalysts, but the prohibitive price and scarce resources greatly limit their large-scale applications. Furthermore, these catalysts typically exhibit high activity for only one half-reaction and poorer activity for the other half-reaction. Therefore, the development of bifunctional non-noble metal compound catalysts with high HER and OER activities is crucial for realizing efficient water electrolysis from two aspects of cost reduction and process simplification.

In terms of cost-effectiveness, catalytic activity, and long-term stability, transition metals or their derivatives such as chalcogenides, nitrides, and phosphides have been widely used as HER catalysts, while perovskites and transition metal hydroxides/oxides Compounds have been widely used as OER catalysts. Nickel-based compounds proved to be promising electrocatalysts for HER and OER due to their earth-abundant, environmentally friendly and easily tunable electronic structures.

Inspired by Ming Gong et al. ( Angew. Chem. , 2015, 127, 12157.) use Cr ₂ O ₃ to passivate Ni/NiO to obtain a highly stable and active HER/OER bifunctional catalyst. It has been reported that VIB group elements in low spin states (such as chromium, molybdenum, and tungsten) can exhibit different oxidation states, and their oxides have reversible surface oxygen-ion exchange capacity (Nature communications, 2014, 5(1): 1-6.). In addition, Ni-NiO heterojunctions have been reported to optimize the hydrogen adsorption energy, thereby accelerating the hydrogen adsorption kinetics (Nature communications, 2014, 5(1): 1-6.).

Accordingly, we plan to use "solution coating + electrochemical reduction" to prepare chromium oxide (molybdenum oxide) passivated nickel/nickel oxide in situ electrodes. Using a relatively negative reduction potential to generate oxides from the attached hydroxide, nickel oxides or nickel salts are reduced to metallic nickel, and more active sites are exposed at the same time; by adjusting the electrochemical reduction time, nickel and oxides in the prepared electrodes are optimized The ratio of nickel, the as-prepared chromium oxide (molybdenum oxide) passivated nickel/nickel oxide in situ electrode is expected to have high HER and OER electrocatalytic activity and high stability.

SUMMARY OF THE INVENTION

In view of this, the present invention provides a method for preparing a chromium oxide (molybdenum oxide) passivated nickel/nickel oxide in-situ electrode, the preparation comprising the following steps:

(1) Preparation of nickel/chromium (molybdenum) (hydro)oxide precursor: Dissolve the decrystallized nickel chloride in a mixture of ethanol and glacial acetic acid, and then add chromium acetate (molybdenum acetylacetonate) while stirring , then add a mixture of water-ethanol, continue to stir until the solution is clear, place the solution in a hydrothermal box to keep warm to form oxides or nickel that mainly contain nickel/chromium (molybdenum) ions and a small amount of nickel/chromium (molybdenum) / Chromium (molybdenum) hydroxide solution (the preparation process of the precursor solution, including the heat preservation process, did not see obvious hydrolysis and deposition, the solution became viscous, and the deposition disappeared, indicating that a large amount of nickel/chromium (molybdenum) is still ionized. The precursor liquid is more like a solution than a sol), and the nickel foam (NF) is immersed in it after cooling, and then taken out to dry.

(2) Electroreduction: The NF attached to the precursor is placed in a mixture of sodium sulfate and boric acid, and the electrochemical workstation is used to electroreduce the NF for a period of time in a potentiostatic manner. Rinse the surface electrolyte with UP water and then dry to obtain a nickel/nickel oxide in situ electrode passivated by chromium oxide (molybdenum oxide).

Further, in S1, the concentration of nickel chloride is 0.5~1 mol/L, the molar ratio of chromium acetate to nickel chloride is 1:0.1~0.3, and the concentration of molybdenum acetylacetonate is 1:0.1~0.2 mol/L.

Further, in S1, the first solvent is the mixed solution of ethanol and glacial acetic acid, wherein the volume ratio of ethanol and glacial acetic acid is 1:0.02～0.04, and the second solvent is the mixed solution of water-ethanol, wherein ethanol and water The volume ratio of the solvent is 1:0.03~0.07, and the volume ratio of the first solvent to the second solvent is 1:0.1~0.3.

Further, the heat preservation temperature of the hydrothermal box described in S1 is 80° C., and the heat preservation time is 4 hours.

Further, the drying described in S1 and S2 is 70°C to 90°C.

Further, in S2, the potential range is -1.0~-2.0 V relative to the saturated calomel electrode.

Further, the time in S2 is 200 seconds to 600 seconds.

The invention also relates to the application of the material obtained by the preparation method in the HER/OER bifunctional catalytic electrolysis of water.

The present invention has the following beneficial effects:

1. The mixture of Ni and Cr(Mo) elements in the precursor solution reaches the molecular level. For the catalytic performance of the subsequently formed heterojunction catalyst, on the one hand, it is beneficial to refine the particle size of the product, which in turn is beneficial to expose more activity. On the other hand, it is convenient for the uniform dispersion of Ni, nickel oxide, and chromium oxide phase (molybdenum oxide phase) in the nickel/nickel oxide in-situ electrode passivated by chromium oxide, which is conducive to obtaining a more abundant interface. Nickel/nickel oxide heterojunction and achieve good coating of chromium oxide (molybdenum oxide) phase, which is beneficial to synergistically improve the electrocatalytic activity and stability of HER and OER.

2. The NF after the attached precursor is placed in a mixed solution of sodium sulfate and boric acid, and the NF is electroreduced for a period of time by a potentiostatic method using an electrochemical workstation. Using the electrochemical reduction mechanism, the oxide is more stable than the hydroxide at a more negative potential, and the phases of chromium oxide (molybdenum oxide) and nickel oxide can be obtained. It is reduced to zero-valent metal nickel.

Description of drawings

Figure 1 shows the HER linear voltammetry curve and the OER linear voltammetry scan measured by the sample prepared in Example 1, wherein a is the HER linear voltammetry scan (LSV), and b is the OER linear voltammetry scan (LSV).

Figure 2 shows the HER linear voltammetry curve and the OER linear voltammetry scan measured by the sample prepared in Example 2, where a is the HER linear voltammetry scan (LSV), and b is the OER linear voltammetry scan (LSV).

3 is the HER linear voltammetry curve and the OER linear voltammetry scan measured by the sample prepared in Example 3, wherein a is the HER linear voltammetry scan (LSV), and b is the OER linear voltammetry scan (LSV).

4 shows the HER linear voltammetry curve and OER linear voltammetry scan measured by the sample prepared in Example 4, wherein a is the HER linear voltammetry scan (LSV), and b is the OER linear voltammetry scan (LSV).

Figure 5 shows the HER linear voltammetry curve and the OER linear voltammetry scan measured by the sample prepared in Example 5, wherein a is the HER linear voltammetry scan (LSV), and b is the OER linear voltammetry scan (LSV).

Figure 6 shows the HER linear voltammetry curve and the OER linear voltammetry scan measured by the sample prepared in Example 6, wherein a is the HER linear voltammetry scan (LSV), and b is the OER linear voltammetry scan (LSV).

Figure 7 shows the HER linear voltammetry curve and the OER linear voltammetry scan measured by the sample prepared in Example 7, wherein a is the HER linear voltammetry scan (LSV), and b is the OER linear voltammetry scan (LSV).

Figure 8 shows the HER linear voltammetry curve and the OER linear voltammetry scan measured by the sample prepared in Example 8, wherein a is the HER linear voltammetry scan (LSV), and b is the OER linear voltammetry scan (LSV).

9 shows the HER linear voltammetry curve and the OER linear voltammetry scan measured by the sample prepared in Example 9, wherein a is the HER linear voltammetry scan (LSV), and b is the OER linear voltammetry scan (LSV).

10 is the HER linear voltammetry curve and the OER linear voltammetry scan measured by the sample prepared in Example 10, wherein a is the HER linear voltammetry scan (LSV), and b is the OER linear voltammetry scan (LSV).

Figure 11 shows the HER linear voltammetry curve and the OER linear voltammetry scan measured by the sample prepared in Example 11, wherein a is the HER linear voltammetry scan (LSV), and b is the OER linear voltammetry scan (LSV).

Figure 12 shows the HER linear voltammetry curve and the OER linear voltammetry scan measured by the sample prepared in Example 12, wherein a is the HER linear voltammetry scan (LSV), and b is the OER linear voltammetry scan (LSV).

13 is the SEM image of the sample prepared in Example 3, a is a 10000 magnification image, and b is a 50000 magnification image.

FIG. 14 is the SEM image of the sample prepared in Example 5, a is a 10000 magnification image, and b is a 20000 magnification image.

FIG. 15 is the SEM image of the sample prepared in Example 6, a is a 10000 magnification image, and b is a 50000 magnification image.

FIG. 16 is the SEM image of the sample prepared in Example 9, a is a 10000 magnification image, and b is a 50000 magnification image.

FIG. 17 is the SEM image of the sample prepared in Example 11, a is a 10000 magnification image, and b is a 50000 magnification image.

18 is the SEM image of the sample prepared in Example 12, a is a 10000 magnification image, and b is a 20000 magnification image.

FIG. 19 is the XRD patterns of Example 3, Example 5, and Example 6. FIG.

FIG. 20 is the XRD patterns of Example 9, Example 11, and Example 12. FIG.

Characterization condition

In the embodiment of the invention, the HER and OER test methods are as follows: the nickel foam is used as the working electrode, the carbon rod is used as the counter electrode, and the saturated Hg/HgO electrode is used as the reference electrode, the electrolyte used is: 1 M KOH aqueous solution, and the scanning speed is 5~ 10 mV/s. Nitrogen was injected in the HER test, and oxygen was injected in the OER test. Oxygen and nitrogen were naturally saturated in 1 M aqueous KOH with stirring at 200 rpm during the test. The saturated Hg/HgO electrode is calibrated with a reversible hydrogen electrode, and the potentials described below are relative to the reversible hydrogen electrode. In the LSV test, the potential ( IR-95% ) compensation was automatically performed by Shanghai Chenhua workstation. X-ray diffraction (SEM) patterns of the samples were obtained using a SMART LAB-9 X-ray diffractometer. Scanning electron microscope (XRD) images were acquired using an Inspect F50 scanning electron microscope (FEI America).

Example 1

At room temperature, 4.125 _g of NiCl2 was dissolved in a mixture of 36.5 mL of ethanol and 1.2 mL of glacial acetic acid, then 1.28 g of chromium acetate was added while stirring, and then a mixture of 10 mL of ethanol and 0.5 mL of water was added dropwise, Continue stirring until the solution is clear and a solution is formed. It was subsequently sealed and incubated in a hydrothermal box at 80°C for 4 hours, and after cooling, the nickel foam (NF) was immersed for ten minutes, followed by drying at 80°C. Weigh 7.102 g of sodium sulfate and 3.0915 g of boric acid to prepare 100 mL of electrolyte, and the solvent is UP water. The treated NF was electroreduced by an electrochemical workstation. The reference electrode was a calomel electrode, and the counter electrode was a platinum sheet. The potential was set to -1.0 V for 600 seconds. Rinse off the surface electrolyte with UP water and dry.

FIG. 1 shows the measured HER and OER linear voltammetry (LSV) scans of the samples prepared in Example 1. It can be seen from Fig. 1(a) that when the current density passing through the electrode is 10 mA/cm ² , the overpotential corresponding to hydrogen production by the HER reaction in the alkaline aqueous solution is 166 mV; from Fig. 1(b), it can be seen that the current density passing through the electrode is At 10 mA/cm ² , the overpotential corresponding to oxygen production by OER reaction in alkaline aqueous solution is 390 mV.

Example 2

At room temperature, 4.125 _g of NiCl2 was dissolved in a mixture of 36.5 mL of ethanol and 1.2 mL of glacial acetic acid, then 1.28 g of chromium acetate was added while stirring, and then a mixture of 10 mL of ethanol and 0.5 mL of water was added dropwise, Continue stirring until the solution is clear and a solution is formed. It was subsequently sealed and incubated in a hydrothermal box at 80°C for 4 hours, and after cooling, the nickel foam (NF) was immersed for ten minutes, followed by drying at 80°C. Weigh 7.102 g of sodium sulfate and 3.0915 g of boric acid to prepare 100 mL of electrolyte, and the solvent is UP water. The treated NF was electroreduced by an electrochemical workstation. The reference electrode was a calomel electrode, and the counter electrode was a platinum sheet. The alternating potential was set, the first stage potential was -1.0 V, the time was 30 seconds, and the second stage potential was +0.3 V, time 5 seconds, alternate cycle 40 times. Rinse off the surface electrolyte with UP water and dry.

FIG. 2 shows the measured HER and OER linear voltammetry (LSV) scans of the samples prepared in Example 2. It can be seen from Figure 2(a) that the overpotential corresponding to the HER reaction in the alkaline aqueous solution is 178 mV when the current density passing through the electrode is 10 mA/cm ² ; The overpotential corresponding to the OER reaction in alkaline aqueous solution is 360 mV at mA/cm ² .

Example 3

At room temperature, 4.125 _g of NiCl2 was dissolved in a mixture of 36.5 mL of ethanol and 1.2 mL of glacial acetic acid, then 1.28 g of chromium acetate was added while stirring, and then a mixture of 10 mL of ethanol and 0.5 mL of water was added dropwise, Continue stirring until the solution is clear and a solution is formed. It was subsequently sealed and incubated in a hydrothermal box at 80°C for 4 hours, and after cooling, the nickel foam (NF) was immersed for ten minutes, followed by drying at 80°C. Weigh 7.102 g of sodium sulfate and 3.0915 g of boric acid to prepare 100 mL of electrolyte, and the solvent is UP water. The treated NF was electroreduced by an electrochemical workstation. The reference electrode was a calomel electrode, and the counter electrode was a platinum sheet. The potential was set at -1.5 V for 200 seconds. Rinse off the surface electrolyte with UP water and dry.

FIG. 3 shows the measured HER and OER linear voltammetry (LSV) scans of the samples prepared in Example 3. FIG. It can be seen from Figure 3(a) that when the current density through the electrode is 10 mA/cm ² , the overpotential corresponding to the HER reaction in the alkaline aqueous solution is 156 mV; from Figure 3(b), it can be seen that when the current density through the electrode is 10 The overpotential corresponding to the OER reaction in alkaline aqueous solution is 380 mV at mA/cm ² .

FIG. 3 is the SEM image of Example 3. It can be seen from the figure that the prepared sample is attached to the nickel foam in a block shape, and it is observed that it has pores under high magnification.

Example 4

At room temperature, 4.125 _g of NiCl2 was dissolved in a mixture of 36.5 mL of ethanol and 1.2 mL of glacial acetic acid, then 1.28 g of chromium acetate was added while stirring, and then a mixture of 10 mL of ethanol and 0.5 mL of water was added dropwise, Continue stirring until the solution is clear and a solution is formed. It was subsequently sealed and incubated in a hydrothermal box at 80°C for 4 hours, and after cooling, the nickel foam (NF) was immersed for ten minutes, followed by drying at 80°C. Weigh 7.102 g of sodium sulfate and 3.0915 g of boric acid to prepare 100 mL of electrolyte, and the solvent is UP water. The treated NF was electroreduced by an electrochemical workstation. The reference electrode was a calomel electrode, and the counter electrode was a platinum sheet. The potential was set at -1.5 V for 400 seconds. Rinse off the surface electrolyte with UP water and dry.

FIG. 4 shows the measured HER and OER linear voltammetry (LSV) scans of the samples prepared in Example 4. FIG. It can be seen from Figure 4(a) that the overpotential corresponding to the HER reaction in the alkaline aqueous solution is 163 mV when the current density passing through the electrode is 10 mA/cm ² ; The overpotential corresponding to the OER reaction in alkaline aqueous solution is 370 mV at mA/cm ² .

Example 5

At room temperature, 4.125 _g of NiCl2 was dissolved in a mixture of 36.5 mL of ethanol and 1.2 mL of glacial acetic acid, then 1.28 g of chromium acetate was added while stirring, and then a mixture of 10 mL of ethanol and 0.5 mL of water was added dropwise, Continue stirring until the solution is clear and a solution is formed. It was subsequently sealed and incubated in a hydrothermal box at 80°C for 4 hours, and after cooling, the nickel foam (NF) was immersed for ten minutes, followed by drying at 80°C. Weigh 7.102 g of sodium sulfate and 3.0915 g of boric acid to prepare 100 mL of electrolyte, and the solvent is UP water. The treated NF was electroreduced by an electrochemical workstation. The reference electrode was a calomel electrode, and the counter electrode was a platinum sheet. The potential was set at -1.5 V for 600 seconds. Rinse off the surface electrolyte with UP water and dry.

FIG. 5 shows the HER and OER linear voltammetry (LSV) scans of the samples prepared in Example 5. FIG. It can be seen from Fig. 5(a) that when the current density passing through the electrode is 10 mA/cm ² , the overpotential corresponding to the HER reaction in the alkaline aqueous solution is 174 mV; from Fig. 5(b), it can be seen that the current density passing through the electrode is 10 mV. The overpotential corresponding to the OER reaction in alkaline aqueous solution is 350 mV at mA/cm ² .

FIG. 5 is the SEM image of Example 5. It can be seen from the figure that the prepared sample is attached to the nickel foam in a block shape, and it is observed in the state of small particles under high magnification.

Example 6

At room temperature, 4.125 _g of NiCl2 was dissolved in a mixture of 36.5 mL of ethanol and 1.2 mL of glacial acetic acid, then 1.28 g of chromium acetate was added while stirring, and then a mixture of 10 mL of ethanol and 0.5 mL of water was added dropwise, Continue stirring until the solution is clear and a solution is formed. It was subsequently sealed and incubated in a hydrothermal box at 80°C for 4 hours, and after cooling, the nickel foam (NF) was immersed for ten minutes, followed by drying at 80°C. Weigh 7.102 g of sodium sulfate and 3.0915 g of boric acid to prepare 100 mL of electrolyte, and the solvent is UP water. The treated NF was electroreduced by an electrochemical workstation. The reference electrode was a calomel electrode, and the counter electrode was a platinum sheet. The potential was set at -2.0 V for 600 seconds. Rinse off the surface electrolyte with UP water and dry.

FIG. 6 shows the measured HER and OER linear voltammetry (LSV) scans of the samples prepared in Example 6. FIG. It can be seen from Figure 6(a) that the overpotential corresponding to the HER reaction in the alkaline aqueous solution is 168 mV when the current density passing through the electrode is 10 mA/cm ² ; it can be seen from Figure 6(b) that the current density passing through the electrode is 10 The overpotential corresponding to the OER reaction in alkaline aqueous solution is 320 mV at mA/cm ² .

FIG. 6 is the SEM image of Example 6. It can be seen from the figure that the prepared sample is attached to the nickel foam, and it is observed to be spherical under high magnification.

Figure 19 shows the XRD patterns of Example 3, Example 5, and Example 6. Compared with the standard PDF card, the three strongest peaks of the pattern are Ni peaks, and the crystallinity of the generated nickel oxide and chromium oxide is not high. The diffraction peaks are very high. weak.

Example 7

At room temperature, dissolve 2.475 g of NiCl ₂ in a mixture of 21.99 mL of ethanol and 0.72 mL of glacial acetic acid, then add 1.099 g of molybdenum acetylacetonate while stirring, and then add dropwise a mixture of 6 mL of ethanol and 0.3 mL of water , continue to stir until the solution is clear and a solution is formed. It was subsequently sealed and incubated in a hydrothermal box at 80°C for 4 hours, and after cooling, the nickel foam (NF) was immersed for ten minutes, followed by drying at 80°C. Weigh 7.102 g of sodium sulfate and 3.0915 g of boric acid to prepare 100 mL of electrolyte, and the solvent is UP water. The treated NF was electroreduced by an electrochemical workstation. The reference electrode was a calomel electrode, and the counter electrode was a platinum sheet. The potential was set at -1.0 V for 600 seconds. Rinse off the surface electrolyte with UP water and dry.

FIG. 7 shows the measured HER and OER linear voltammetry (LSV) scans of the samples prepared in Example 7. FIG. It can be seen from Figure 7(a) that the overpotential corresponding to the HER reaction in the alkaline aqueous solution is 163 mV when the current density passing through the electrode is 10 mA/cm ² ; it can be seen from Figure 7(b) that the current density passing through the electrode is 10 The overpotential corresponding to the OER reaction in alkaline aqueous solution is 370 mV at mA/cm ² .

Example 8

At room temperature, dissolve 2.475 g of NiCl ₂ in a mixture of 21.99 mL of ethanol and 0.72 mL of glacial acetic acid, then add 1.099 g of molybdenum acetylacetonate while stirring, and then add dropwise a mixture of 6 mL of ethanol and 0.3 mL of water , continue to stir until the solution is clear and a solution is formed. It was subsequently sealed and incubated in a hydrothermal box at 80°C for 4 hours, and after cooling, the nickel foam (NF) was immersed for ten minutes, followed by drying at 80°C. Weigh 7.102 g of sodium sulfate and 3.0915 g of boric acid to prepare 100 mL of electrolyte, and the solvent is UP water. The treated NF was electroreduced by an electrochemical workstation. The reference electrode was a calomel electrode and a platinum sheet was used for the counter electrode. The first section of alternating potential was set to -1.0 V for 30 seconds, and the second section of potential was +0.3 V. , the time is 5 seconds, and the cycle is repeated 40 times. Rinse off the surface electrolyte with UP water and dry.

FIG. 8 shows the measured HER and OER linear voltammetry (LSV) scans of the samples prepared in Example 8. FIG. It can be seen from Figure 8(a) that the overpotential corresponding to the HER reaction in the alkaline aqueous solution is 174 mV when the current density passing through the electrode is 10 mA/cm ² ; it can be seen from Figure 8(b) that the current density passing through the electrode is 10 The overpotential corresponding to the OER reaction in alkaline aqueous solution is 390 mV at mA/cm ² .

Example 9

At room temperature, 2.475 _g of NiCl was dissolved in a mixture of 21.99 mL of ethanol and 0.72 mL of glacial acetic acid, then 1.099 g of molybdenum acetylacetonate was added while stirring, and then a mixture of 6 mL of ethanol and 0.3 mL of water was added dropwise , continue to stir until the solution is clear and a solution is formed. It was subsequently sealed and incubated in a hydrothermal box at 80°C for 4 hours, and after cooling, the nickel foam (NF) was immersed for ten minutes, followed by drying at 80°C. Weigh 7.102 g of sodium sulfate and 3.0915 g of boric acid to prepare 100 mL of electrolyte, and the solvent is UP water. The treated NF was electroreduced by an electrochemical workstation. The reference electrode was a calomel electrode, and the counter electrode was a platinum sheet. The potential was set at -1.5 V for 200 seconds. Rinse off the surface electrolyte with UP water and dry.

FIG. 9 shows the measured HER and OER linear voltammetry (LSV) scans of the samples prepared in Example 9. FIG. It can be seen from Figure 9(a) that the overpotential corresponding to the HER reaction in the alkaline aqueous solution is 155 mV when the current density passing through the electrode is 10 mA/cm ² ; The overpotential corresponding to the OER reaction in alkaline aqueous solution is 350 mV at mA/cm ² .

FIG. 16 is the SEM image of Example 9. It can be seen from the figure that the prepared sample is attached to the nickel foam, and it is observed to be spherical under high magnification.

Example 10

At room temperature, dissolve 2.475 g of NiCl ₂ in a mixture of 21.99 mL of ethanol and 0.72 mL of glacial acetic acid, then add 1.099 g of molybdenum acetylacetonate while stirring, and then add dropwise a mixture of 6 mL of ethanol and 0.3 mL of water , continue to stir until the solution is clear and a solution is formed. It was subsequently sealed and incubated in a hydrothermal box at 80°C for 4 hours, and after cooling, the nickel foam (NF) was immersed for ten minutes, followed by drying at 80°C. Weigh 7.102 g of sodium sulfate and 3.0915 g of boric acid to prepare 100 mL of electrolyte, and the solvent is UP water. The treated NF was electroreduced by an electrochemical workstation. The reference electrode was a calomel electrode, and the counter electrode was a platinum sheet. The potential was set at -1.5 V for 400 seconds. Rinse off the surface electrolyte with UP water and dry.

FIG. 10 shows the measured HER and OER linear voltammetry (LSV) scans of the samples prepared in Example 10. It can be seen from Figure 10(a) that the overpotential corresponding to the HER reaction in the alkaline aqueous solution is 175 mV when the current density passing through the electrode is 10 mA/cm ² ; it can be seen from Figure 10(b) that the current density passing through the electrode is 10 The overpotential corresponding to the OER reaction in alkaline aqueous solution is 330 mV at mA/cm ² .

Example 11

At room temperature, dissolve 2.475 g of NiCl ₂ in a mixture of 21.99 mL of ethanol and 0.72 mL of glacial acetic acid, then add 1.099 g of molybdenum acetylacetonate while stirring, and then add dropwise a mixture of 6 mL of ethanol and 0.3 mL of water , continue to stir until the solution is clear and a solution is formed. It was subsequently sealed and incubated in a hydrothermal box at 80°C for 4 hours, and after cooling, the nickel foam (NF) was immersed for ten minutes, followed by drying at 80°C. Weigh 7.102 g of sodium sulfate and 3.0915 g of boric acid to prepare 100 mL of electrolyte, and the solvent is UP water. The treated NF was electroreduced by an electrochemical workstation. The reference electrode was a calomel electrode, and the counter electrode was a platinum sheet. The potential was set at -1.5 V for 600 seconds. Rinse off the surface electrolyte with UP water and dry.

FIG. 11 shows the measured HER and OER linear voltammetry (LSV) scans of the samples prepared in Example 11. It can be seen from Fig. 11(a) that the overpotential corresponding to the HER reaction in the alkaline aqueous solution is 139 mV when the current density passing through the electrode is 10 mA/cm ² ; The overpotential corresponding to the OER reaction in alkaline aqueous solution is 350 mV at mA/cm ² .

FIG. 17 is the SEM image of Example 11. It can be seen from the figure that the prepared sample is attached to the nickel foam, and it is observed to be spherical under high magnification.

Example 12

At room temperature, dissolve 2.475 g of NiCl ₂ in a mixture of 21.99 mL of ethanol and 0.72 mL of glacial acetic acid, then add 1.099 g of molybdenum acetylacetonate while stirring, and then add dropwise a mixture of 6 mL of ethanol and 0.3 mL of water , continue to stir until the solution is clear and a solution is formed. It was subsequently sealed and incubated in a hydrothermal box at 80°C for 4 hours, and after cooling, the nickel foam (NF) was immersed for ten minutes, followed by drying at 80°C. Weigh 7.102 g of sodium sulfate and 3.0915 g of boric acid to prepare 100 mL of electrolyte, and the solvent is UP water. The treated NF was electroreduced by an electrochemical workstation. The reference electrode was a calomel electrode, and the counter electrode was a platinum sheet. The potential was set at -2.0 V for 600 seconds. Rinse off the surface electrolyte with UP water and dry.

FIG. 12 shows the measured HER and OER linear voltammetry (LSV) scans of the samples prepared in Example 12. It can be seen from Fig. 12(a) that the overpotential corresponding to the HER reaction in the alkaline aqueous solution is 150 mV when the current density passing through the electrode is 10 mA/cm ² ; The overpotential corresponding to the OER reaction in alkaline aqueous solution is 350 mV at mA/cm ² .

FIG. 18 is the SEM image of Example 12, in which it can be seen that the prepared sample is attached to the nickel foam, and it is observed to be spherical at high magnification.

Fig. 20 is the XRD pattern of Example 3, Example 5, and Example 6. Compared with the standard PDF card, the three strongest peaks from the pattern are Ni peaks, and the crystallinity of the generated nickel oxide and molybdenum oxide is not high. very weak.

Example 13

At room temperature, dissolve 0.825 _g of NiCl2 in a mixture of 7.3 mL of ethanol and 0.24 mL of glacial acetic acid, then add 0.366 g of molybdenum acetylacetonate while stirring, and then add dropwise a mixture of 2 mL of ethanol and 0.1 mL of water , continue to stir until the solution is clear and a solution is formed. It was then sealed and incubated in a hydrothermal box at 120 °C for 4 hours, and after cooling, the nickel foam (NF) was immersed for ten minutes, followed by drying at 80 °C. Weigh 7.102 g of sodium sulfate and 3.0915 g of boric acid to prepare 100 mL of electrolyte, and the solvent is UP water. The treated NF was electroreduced by an electrochemical workstation. The reference electrode was a calomel electrode, and the counter electrode was a platinum sheet. The potential was set at -3.0 V for 1800 seconds. Rinse the surface electrolyte with UP water and dry.

When the current density through the electrode is 10 mA/cm ² , the overpotential corresponding to the HER reaction in the alkaline aqueous solution is 210 mV; when the current density through the electrode is 10 mA/cm ² , the OER reaction in the alkaline aqueous solution corresponds to the overpotential The overpotential is 300mV.

Example 14

At room temperature, 0.825 _g of NiCl2 was dissolved in a mixture of 7.3 mL of ethanol and 0.24 mL of glacial acetic acid, then 0.146 g of chromium acetate was added while stirring, and then a mixture of 2 mL of ethanol and 0.1 mL of water was added dropwise, Continue stirring until the solution is clear and a solution is formed. It was then sealed and incubated in a hydrothermal box at 120 °C for 4 hours, and after cooling, the nickel foam (NF) was immersed for ten minutes, followed by drying at 80 °C. Weigh 7.102 g of sodium sulfate and 3.0915 g of boric acid to prepare 100 mL of electrolyte, and the solvent is UP water. The treated NF was electroreduced by an electrochemical workstation. The reference electrode was a calomel electrode, and the counter electrode was a platinum sheet. The potential was set at -3.0 V for 1800 seconds. Rinse off the surface electrolyte with UP water and dry.

When the current density through the electrode is 10 mA/cm ² , the overpotential corresponding to the HER reaction in the alkaline aqueous solution is 203 mV; when the current density through the electrode is 10 mA/cm ² , the OER reaction in the alkaline aqueous solution corresponds to the overpotential of 203 mV. The overpotential is 300mV.

Claims (4)

1. A preparation method of a metal oxide passivated nickel/nickel oxide in-situ electrode is characterized by comprising the following steps:

s1, preparing an oxide or hydroxide precursor of nickel/chromium: dissolving nickel chloride with crystal water removed in a first solvent, adding chromium acetate while stirring, then adding a second solvent, continuously stirring until the solution is clear, placing the solution in a hydrothermal box, keeping the temperature at 80-120 ℃, keeping the temperature for 4 hours to form a solution containing nickel/chromium oxide or hydroxide, cooling, then soaking foamed nickel in the solution, and then taking out and drying;

the first solvent is a mixed solution of ethanol and glacial acetic acid, wherein the volume ratio of the ethanol to the glacial acetic acid is 1: 0.02-0.04, wherein the second solvent is a water-ethanol mixed solution, and the volume ratio of ethanol to water is 1: 0.03-0.07, wherein the volume ratio of the first solvent to the second solvent is 1: 0.1-0.3, the concentration of nickel chloride is 0.5-1 mol/L, and the molar ratio of chromium acetate to nickel chloride is 1: 0.1 to 0.3;

s2, electroreduction: and (2) placing the NF attached with the precursor in an electrolyte of sodium sulfate and boric acid, performing electro-reduction on the NF for a period of time by using an electrochemical workstation in a constant potential mode, wherein the constant potential is in a range of-1.0 to-2.0V relative to the saturated calomel electrode, flushing the electrolyte on the surface by UP water, and drying to obtain the chromium oxide passivated nickel/nickel oxide in-situ electrode.

2. The method of claim 1, wherein the drying in S1 and S2 is 70-90 ℃.

3. The method for preparing the metal oxide passivated nickel/nickel oxide in-situ electrode according to claim 1, wherein the time in S2 is 200 seconds to 600 seconds.

4. The method of claim 1, wherein the chromium acetate is replaced by molybdenum acetylacetonate, and the molar ratio of molybdenum acetylacetonate to nickel chloride is 1: 0.1-0.2, the obtained product is a nickel/nickel oxide in-situ electrode passivated by molybdenum oxide.

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