Preparation method of nickel-based heterojunction composite catalytic electrode for hydrogen evolution

Abstract

The invention relates to a preparation method of a nickel-based heterojunction composite catalytic electrode for hydrogen evolution, and belongs to the technical field of electro-catalysis. According to the method, the CC / NiCo-NiCo (OH) 2 electrode is prepared by regulating the pH value of the electrolyte and utilizing a local alkalescence environment generated by one-step electrodeposition, and the CC / NiCo-NiCo (OH) 2 electrode has a unique structure that NiCo layered metal hydroxide wraps NiCo alloy and has relatively large specific surface area and charge transfer capacity; the CC / NiCo-NiCo (OH) 2 electrode is phosphatized to obtain the CC / NiCo-NiCoP electrode, so that the electronic structure of the material is optimized, more defects are introduced, active sites are increased, and the gas desorption performance is improved; the nickel-based heterojunction composite catalytic electrode CC / NiCo-NiCoP / NiOx for hydrogen evolution is obtained through secondary electro-deposition of the CC / NiCo-NiCoP electrode, the surface NiOx layer plays a role in protecting the CC / NiCo-NiCoP electrode, and the corrosion resistance and cycling stability of the catalyst are improved.

Description

Technical Field

[0001] The invention relates to a method for preparing a nickel-based heterojunction composite catalytic electrode for hydrogen evolution, belonging to the technical field of electrocatalysis. Background Art

[0002] In the electrolysis of water to produce hydrogen, the main factor affecting energy consumption is largely restricted by the overpotential. Improving the transfer of electrons during the reaction and reducing the reaction overpotential can greatly reduce the energy consumption of water electrolysis. Precious metals Ir, Ru, Pt and their oxides have excellent performance in electrocatalytic hydrogen production, but are difficult to promote and use on a large scale due to their high cost and low reserves. Transition metals such as Fe, Co, and Ni have high electrocatalytic activity, and their costs can be reduced by several times compared to precious metals, but the catalytic activity of a single metal still lags far behind that of precious metals. Multi-component alloys can greatly improve the catalytic activity of the material due to the synergistic effect between the metals. At the same time, the unique heterogeneous interface can accelerate the desorption of hydrogen, increase the contact interface and time between the catalyst and water, and thus accelerate the hydrogen production rate. At the same time, the introduction of non-metallic elements such as P, S and Se can increase the defect density and effectively improve the active sites.

[0003] Conventional hydrogen evolution catalysts rely on rare and precious metals such as platinum, which are scarce and expensive, significantly limiting their large-scale industrial application. While some non-precious transition metal-based catalysts offer lower costs, they suffer from a limited number of active sites and poor catalytic performance, making efficient hydrogen evolution reactions difficult. Furthermore, in the actual electrolysis of water, some catalysts are susceptible to factors such as corrosion and agglomeration, leading to changes in their structure and performance, making them unable to operate stably for extended periods. For example, in acidic conditions, alloy catalysts based primarily on non-precious metal elements can suffer from corrosion and reduced stability. However, alloying can modulate the electronic structure of the catalyst, changing the electron cloud distribution on the catalyst surface, thereby optimizing the adsorption and desorption properties of intermediates and enhancing catalytic activity. For example, ruthenium-alloyed iron phosphide single crystals increase the Fermi level through alloying, improving the intrinsic performance of the hydrogen evolution reaction. The introduction of phosphorus can also alter the catalyst's crystal structure, increasing the number and activity of active sites. Furthermore, phosphides generally have good electrical conductivity, which promotes electron transport and facilitates the hydrogen evolution reaction. When composite materials, especially metal oxides, form composite structures with metals (alloys) or other substances, a synergistic effect occurs at the interface. For example, in common metal oxide / alloy composite catalysts, there is a "chimney effect" at the interface. The special chemical environment around the interface enables adjacent sites to selectively adsorb hydrogen intermediates, while facilitating the adsorption of reactants and the desorption of products. The oxygen vacancies in metal oxides can improve the conductivity of the catalyst and enhance its ability to adsorb water, while other components in the composite structure may promote processes such as the dissociation of water, thereby accelerating the hydrogen evolution reaction. In addition, the hierarchical structure formed by nesting metal or alloy nanostructures into other catalysts can also enhance the cohesion between the metal catalyst and the carrier, improve the dispersion and stability of the catalyst, and help improve the electrocatalytic performance. Summary of the Invention

[0004] In view of the problems of high cost, low activity and poor stability of existing hydrogen evolution catalysts, the present invention proposes a method for preparing a nickel-based heterojunction composite catalytic electrode for hydrogen evolution. By regulating the pH of the electrolyte and utilizing the local weak alkaline environment generated by one-step electrodeposition, a CC / NiCo@NiCo(OH)2 electrode is prepared. The CC / NiCo@NiCo(OH)2 electrode has a unique structure of NiCo layered metal hydroxide wrapped in NiCo alloy, and has a large specific surface area and charge transfer capacity. After annealing and phosphating, a CC / NiCo@NiCoP electrode is obtained. The introduction of P element optimizes the electronic structure of the material and improves the gas desorption performance. The CC / NiCo@NiCoP electrode is subjected to secondary electrodeposition to obtain CC / NiCo@NiCoP / NiO x Nickel-based heterojunction composite catalytic electrode for hydrogen evolution, NiO on the surface xThe layer protects the CC / NiCo@NiCoP electrode and improves the corrosion resistance and cycle stability of the catalyst.

[0005] A method for preparing a nickel-based heterojunction composite catalytic electrode for hydrogen evolution, comprising the following steps:

[0006] (1) placing a carbon cloth electrode in an HCl solution for heating and activation, taking it out, washing it with deionized water, and drying it to obtain an activated carbon cloth electrode;

[0007] (2) At room temperature and under stirring conditions, CoSO4·7H2O, NiSO4·6H2O, citric acid, boric acid, L-ascorbic acid and KCl were dissolved in deionized water to obtain a mixed solution. Nitrogen was continuously introduced into the mixed solution for 30-60 min, and the pH of the mixed solution was adjusted to 4-5 using NH4OH to obtain a Co / Ni electrolyte. If the pH value of the Co / Ni electrolyte is too high, the metal ions will easily form hydroxide precipitation directly, while if it is too low, only a separate alloy can be obtained. When the pH value is 4-5, a local weak alkaline environment is formed after electrodeposition, and CC / NiCo@NiCo(OH)2 electrodes can be obtained by electrodeposition. The unique structure of NiCo alloy wrapped by NiCo layered metal hydroxide has a large specific surface area and charge transfer capacity.

[0008] (3) Using an activated carbon cloth electrode as the cathode, a graphite electrode as the anode, and a mercurous sulfate electrode as the reference electrode, a CC / NiCo@NiCo(OH)2 electrode, i.e., a CC / NiCo@NiCo LDH composite electrode, was obtained by electrodeposition in a Co / Ni electrolyte at room temperature;

[0009] (4) placing the CC / NiCo@NiCo(OH)2 electrode and sodium dihydrogen phosphate in a container and annealing for 2-3 h in a nitrogen atmosphere to obtain a CC / NiCo@NiCoP electrode;

[0010] (5) Using CC / NiCo@NiCoP electrode as cathode, graphite electrode as anode, and mercurous sulfate electrode as reference electrode, nickel-based heterojunction composite catalytic electrode CC / NiCo@NiCoP / NiO for hydrogen evolution was obtained by electrodeposition in NiSO4 solution at room temperature. x .

[0011] Preferably, the concentration of the HCl solution in step (1) is 1-3 mol / L, the activation temperature is 70-80° C., and the activation time is 5-8 h.

[0012] Preferably, in the Co / Ni electrolyte of step (2), the CoSO4 concentration is 0.15-0.30 mol / L, the NiSO4 concentration is 0.15-0.30 mol / L, the citric acid concentration is 0.3-0.4 mol / L, the boric acid concentration is 0.4-0.5 mol / L, the L ascorbic acid concentration is 0.005-0.01 mol / L, and the KCl concentration is 0.2-0.3 mol / L.

[0013] Preferably, the potential of the electrodeposition in step (3) is -3 to -5 V, and the deposition time is 10 to 20 minutes.

[0014] Preferably, the amount of sodium dihydrogen phosphate used in step (4) is 0.5-1.0 g, the heating rate is 4-5° C. / min, and the holding temperature is 300-400° C.

[0015] Preferably, the concentration of the NiSO4 solution in step (5) is 0.15-0.30 mol / L, and the pH value is 2-3.

[0016] More preferably, the potential of the electrodeposition in step (5) is -3 to -5 V, and the deposition time is 10 to 20 minutes.

[0017] The beneficial effects of the present invention are:

[0018] (1) The present invention prepares CC / NiCo@NiCo LDH composite catalytic electrodes by one-step electrodeposition by regulating the pH of the electrolyte. The layered structure of the layered metal hydroxide has a large specific surface area, effectively providing active sites. The pH value of the electrolyte is controlled to be 4-5, and the change of the local pH of the electrolyte during the electrodeposition process is a weakly alkaline environment, which is conducive to the preparation of multiple composite catalytic electrodes.

[0019] (2) The phosphated NiCo@NiCoP layered heterogeneous structure of the present invention, in which NiCoP encapsulates NiCo to form a unique undulating structure, provides a disturbance during the flow of the electrolyte, accelerates the uniformity of the electrolyte, and promotes contact with the catalyst;

[0020] (3) The P element of the present invention can undergo interfacial atomic diffusion during water electrolysis, introduce more point defects, increase active sites, achieve improved hydrogen evolution performance, and accelerate hydrogen desorption;

[0021] (4) The NiCo alloy layer of the present invention can effectively improve the charge transport between the carbon cloth electrode and the catalyst. x The layer effectively improves the cyclic stability of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a process flow chart of the present invention;

[0023] Figure 2 This is the SEM image of the comparative example 6CC / NiCo@NiCo LDH composite electrode;

[0024] Figure 3 This is the SEM image of the comparative example 5CC / NiCo@NiCoP electrode;

[0025] Figure 4 Example 1: Nickel-based heterojunction composite catalytic electrode CC / NiCo@NiCoP / NiO for hydrogen evolution x XRD pattern of

[0026] Figure 5 The electrode CC / NiCo@NiCoP / NiO in Example 1 x SEM image at low magnification;

[0027] Figure 6 The electrode CC / NiCo@NiCoP / NiO in Example 1 x SEM images at high magnification;

[0028] Figure 7 The electrode CC / NiCo@NiCoP / NiO in Example 1 x TEM image at low magnification;

[0029] Figure 8 The electrode CC / NiCo@NiCoP / NiO in Example 1 x TEM image at high magnification;

[0030] Figure 9 The electrode CC / NiCo@NiCoP / NiO in Example 1 x HR-TEM image at high magnification;

[0031] Figure 10 The electrode CC / NiCo@NiCoP / NiO in Examples 1, 3, 4 and Comparative Example 3 x Polarization curve diagram. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0033] Example: A method for preparing a nickel-based heterojunction composite catalytic electrode for hydrogen evolution, the specific steps are as follows:

[0034] (1) placing a carbon cloth electrode in an HCl solution for heating and activation, taking it out, washing it with deionized water, and drying it to obtain an activated carbon cloth electrode; the HCl solution concentration is 3 mol / L, the activation temperature is 70°C, and the activation time is 5 h;

[0035] (2) At room temperature and under stirring conditions, CoSO4·7H2O, NiSO4·6H2O, citric acid, boric acid, L ascorbic acid and KCl were dissolved in deionized water to obtain a mixed solution, nitrogen was continuously introduced into the mixed solution for 30 minutes, and the pH of the mixed solution was adjusted to 4-5 with NH4OH to obtain a Co / Ni electrolyte; the Co / Ni electrolyte had a CoSO4 concentration of 0.25 mol / L, a NiSO4 concentration of 0.25 mol / L, a citric acid concentration of 0.25 mol / L, a boric acid concentration of 0.5 mol / L, a L ascorbic acid concentration of 0.1 mol / L, and a KCl concentration of 0.3 mol / L;

[0036] (3) Using an activated carbon cloth electrode as a cathode, a graphite electrode as an anode, and a mercurous sulfate electrode as a reference electrode, electrodeposition was performed in a Co / Ni electrolyte at room temperature to obtain a CC / NiCo@NiCo(OH)2 electrode, i.e., a CC / NiCo@NiCo LDH composite electrode, denoted as electrode A; the electrodeposition potential was -3 to -5 V, and the deposition time was 10 to 20 min;

[0037] (4) placing a CC / NiCo@NiCo(OH)2 electrode and sodium dihydrogen phosphate in a container, annealing and holding for 2-3 h in a nitrogen atmosphere to obtain a CC / NiCo@NiCoP electrode, denoted as electrode B; the amount of sodium dihydrogen phosphate added was 0.5 g, the heating rate was 4.5°C / min, and the holding temperature was 300-400°C;

[0038] (5) Using CC / NiCo@NiCoP electrode as cathode, graphite electrode as anode, and mercurous sulfate electrode as reference electrode, nickel-based heterojunction composite catalytic electrode CC / NiCo@NiCoP / NiO for hydrogen evolution was obtained by electrodeposition in NiSO4 solution at room temperature. x , denoted as electrode C; the concentration of the NiSO4 solution is 0.25 mol / L, the pH value is 2 to 3; the electrodeposition potential is -3 to -5 V, and the deposition time is 10 to 20 min;

[0039] The specific parameters in Examples 1 to 5 are shown in Table 1 below.

[0040] Table 1 Process parameters of Examples 1 to 5

[0041]

[0042] Comparative Examples 1 to 6 are set, and their process parameters are shown in Table 2;

[0043] Table 2 Comparative Example Process Parameters

[0044]

[0045]

[0046] Comparative Example 5 is a CC / NiCo@NiCoP electrode, and Comparative Example 6 is a CC / NiCo@NiCo LDH electrode;

[0047] XRD characterization: Example 1 Nickel-based heterojunction composite catalytic electrode CC / NiCo@NiCoP / NiO for hydrogen evolution x The XRD pattern of Figure 4 The peak around 25° in the figure comes from the carbon cloth peak, which proves the existence of the carbon cloth electrode. In addition to the carbon peak, obvious diffraction peaks are only observed at around 45°, 52° and 76° in the sample, and the main peaks of Ni and Co are just near these peaks, indicating that Ni-Co alloy exists in the sample after electrodeposition. At the same time, the diffraction peak intensity of each peak is low, and no obvious phosphide peak is observed, indicating that the crystallinity of other substances is weak.

[0048] SEM characterization: SEM image of comparative example 6CC / NiCo@NiCo LDH composite electrode is shown in Figure 2 , SEM image of comparative example 5CC / NiCo@NiCoP electrode is shown in Figure 3 ,CC / NiCo@NiCoP / NiO x SEM images of the composite catalyst Figures 5-6 As shown in the figure, the catalyst on the surface of the carbon cloth electrode has more granular and lamellar structures. The granular structure is the NiCo catalyst obtained by initial electrodeposition, while the lamellar structure on the surface is the layered NiCoP catalyst obtained after NiCo LDH phosphating. Therefore, the overall catalytic electrode presents a structure of layered NiCoP wrapped NiCo, in which there are also some granular NiO x .

[0049] TEM characterization: CC / NiCo@NiCoP / NiO x TEM of the composite catalyst Figures 7-8 As shown, the electrode CC / NiCo@NiCoP / NiO x HR-TEM images at high magnification are shown in Figure 9 The sample is granular, and the surface of the granular sample is covered by layered and even finer granular catalysts. The central sample is NiCo alloy, the layered structure is NiCoP material, and the fine granular catalyst is NiO x TEM results show that CC / NiCo@NiCoP / NiO was successfully achieved by electrodeposition. x Preparation of composite catalysts.

[0050] Electrochemical performance characterization:

[0051] A 1.0 M KOH solution was prepared, a graphite electrode was used as the counter electrode, an Ag / AgCl electrode was used as the reference electrode, and the catalytic electrodes obtained in Examples 1 to 4 and Comparative Examples 1 to 6 were used as the working electrode. The samples were connected to an electrochemical workstation and subjected to hydrogen evolution electrochemical performance testing. Electrode activation and impedance measurement were performed before the test to facilitate subsequent IR compensation. After the test, a reversible hydrogen electrode calibration was performed.

[0052] Taking the composite catalytic electrodes prepared in Example 1, Example 3, Example 4 and Comparative Example 3 as examples, the polarization curves are as follows: Figure 10 The test results of Examples 1 to 4 and Comparative Examples 1 to 6 are shown in Table 3;

[0053] Table 3 Electrochemical performance of Examples 1 to 5 and Comparative Examples 1 to 6

[0054]

[0055] CC / NiCo@NiCoP / NiO prepared by electrodeposition combined with phosphating in the embodiment x The composite electrocatalyst, with its layered, particle-encapsulated structure, provides a large specific surface area, exposing more active sites. The complementary strengths of different catalysts accelerate electron transport and accumulation at the interface. Phosphating improves the electronic structure of the catalyst, enhancing catalytic performance and accelerating hydrogen desorption. Furthermore, DC electrodeposition requires simple equipment and is easy to operate, enabling mass production.

[0056] The above describes the specific embodiments of the present invention in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.

Claims

1. A method for preparing a nickel-based heterojunction composite catalytic electrode for hydrogen evolution, characterized in that: The specific steps are as follows: (1) placing a carbon cloth electrode in an HCl solution for heating and activation, taking it out, washing it with deionized water, and drying it to obtain an activated carbon cloth electrode; (2) CoSO4·7H2O, NiSO4·6H2O, citric acid, boric acid, L-ascorbic acid, and KCl were dissolved in deionized water at room temperature with stirring to obtain a mixed solution, nitrogen was continuously introduced into the mixed solution for 30 to 60 minutes, and the pH of the mixed solution was adjusted to 4 to 5 with NH4OH to obtain a Co / Ni electrolyte; (3) Using an activated carbon cloth electrode as the cathode, a graphite electrode as the anode, and a mercurous sulfate electrode as the reference electrode, CC / NiCo@NiCo(OH)2 electrodes were obtained by electrodeposition in a Co / Ni electrolyte at room temperature. (4) placing the CC / NiCo@NiCo(OH)2 electrode and sodium dihydrogen phosphate in a container and annealing for 2-3 h in a nitrogen atmosphere to obtain a CC / NiCo@NiCoP electrode; (5) Using CC / NiCo@NiCoP electrode as cathode, graphite electrode as anode, and mercurous sulfate electrode as reference electrode, nickel-based heterojunction composite catalytic electrode CC / NiCo@NiCoP / NiO for hydrogen evolution was obtained by electrodeposition in NiSO4 solution at room temperature. x .

2. The method for preparing a nickel-based heterojunction composite catalytic electrode for hydrogen evolution according to claim 1, characterized in that: Step (1) The concentration of the HCl solution is 1-3 mol / L, the activation temperature is 70-80° C., and the activation time is 5-8 h.

3. The method for preparing a nickel-based heterojunction composite catalytic electrode for hydrogen evolution according to claim 1, characterized in that: In step (2), the CoSO4 concentration in the Co / Ni electrolyte is 0.15-0.30 mol / L, the NiSO4 concentration is 0.15-0.30 mol / L, the citric acid concentration is 0.3-0.4 mol / L, the boric acid concentration is 0.4-0.5 mol / L, the L ascorbic acid concentration is 0.005-0.01 mol / L, and the KCl concentration is 0.2-0.3 mol / L.

4. The method for preparing a nickel-based heterojunction composite catalytic electrode for hydrogen evolution according to claim 1, characterized in that: The potential of the electroplating in step (3) is -3 to -5 V, and the deposition time is 10 to 20 minutes.

5. The method for preparing the nickel-based heterojunction composite catalytic electrode for hydrogen evolution according to claim 1, characterized in that: The amount of sodium dihydrogen phosphate used in step (4) is 0.5-1.0 g, the heating rate is 4-5° C. / min, and the insulation temperature is 300-400° C.

6. The method for preparing a nickel-based heterojunction composite catalytic electrode for hydrogen evolution according to claim 1, characterized in that: The concentration of the NiSO4 solution in step (5) is 0.15-0.30 mol / L, and the pH value is 2-3.

7. The method for preparing a nickel-based heterojunction composite catalytic electrode for hydrogen evolution according to claim 6, characterized in that: The potential of the electroplating in step (5) is -3 to -5 V, and the deposition time is 10 to 20 minutes.

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