Hierarchical Structure NiO x / Preparation Method and Application of CoP Self-Supported Electrode

Abstract

The present invention relates to a hierarchical structure NiO x / CoP self-supporting electrode and its application in the field of hydrogen energy technology. It includes the following steps: The first step: preparing highly conductive nickel foam; The second step: preparing NiO x nanotube arrays; The third step: preparing a hierarchical structure NiO x / CoP self-supporting electrode. This electrode exhibits excellent catalytic performance in the hydrogen evolution reaction: in a 1 M KOH solution, overpotentials of only 51 and 164 mV are required respectively to reach current densities of 10 and 500 mA cm ‑2 ; the Faraday efficiency is as high as 96%; after 50 h of continuous electrolysis at a constant potential of 51 mV, the potential does not increase significantly, showing excellent stability. The present invention can also be extended to the design of other catalytic materials, providing new ideas for the development of highly efficient and low-cost catalysts.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen energy, and relates to a hierarchical structure NiO x / CoP self-supporting electrode and its application in the technical field of hydrogen energy. Background Technique

[0002] As an energy carrier for the conversion of renewable energy and electric energy, hydrogen energy can achieve efficient and large-scale energy storage, and is an important carrier support for the green and low-carbon transformation of energy-consuming terminals. Alkaline water electrolysis based on renewable energy to produce "green hydrogen" is a clean and sustainable method for preparing hydrogen.

[0003] In recent years, in order to reduce the cost of hydrogen production and improve the hydrogen production efficiency, researchers at home and abroad have developed several types of non-noble metal hydrogen evolution catalysts to replace noble metals, such as transition metal sulfides, selenides, borides, carbides, and phosphides. Among these catalysts, transition metal phosphides, especially CoP-based materials, have attracted much attention due to the following advantages: i) abundant in quantity and low in price; ii) the catalyst maintains high stability in a relatively wide pH range; iii) phosphorus has an appropriate adsorption energy with the intermediate product (H) of the hydrogen evolution reaction. This makes CoP often exhibit outstanding hydrogen evolution catalytic performance in acidic environments. However, the intrinsic hydrogen evolution performance of CoP under alkaline conditions is not satisfactory, mainly because in an alkaline environment, the efficiency of the hydrogen evolution reaction mainly depends on the dissociation of H2O by the catalyst and the adsorption / desorption ability of the catalyst to H2O, H, and OH, while in acidic conditions, it only depends on the adsorption ability of the catalyst to H. The traditional method for preparing CoP is usually to carry out high-temperature (above 200 °C) phosphidation treatment of cobalt oxide together with red phosphorus or sodium hypophosphite. High temperature not only requires additional energy, but also produces highly toxic PH3 gas, which will endanger human health and damage the environment; while the traditional method for preparing NiO x is mostly high-temperature oxidation of nickel metal or high-temperature heat treatment of nickel hydroxide, both of which involve high-temperature treatment. During the high-temperature treatment process, not only a large amount of energy is required, but also high-temperature treatment is likely to cause NiO xSintering and structural collapse. In addition, traditional and currently used powder electrodes often require the addition of polymer binders during the preparation process, and these polymer binders are usually insulators. Their addition not only causes a large contact resistance at the interface of the conductive agent / nano-active phase / current collector but also buries catalytic active sites, thus greatly reducing the hydrogen evolution performance of the electrode. In addition, there is a relatively poor linear relationship between the intermediate products H and OH in alkaline HER, so it is difficult to achieve an ideal catalytic hydrogen production effect by using traditional strategies to increase catalytic active sites. Therefore, while ensuring a large number of catalytic active sites, significantly improving the intrinsic catalytic activity of alkaline HER catalytic materials is the key point and difficulty in enhancing their performance. This is also the reason why most traditional and existing CoP-based materials exhibit poor alkaline HER activity. That is, the alkaline hydrogen evolution activity of the vast majority of CoP-based materials still requires overpotentials of more than 60 mV and more than 250 mV to reach current densities of 10 and 500 mA cm -2 of the current density, and the poor catalytic activity severely limits their commercial application process. Summary of the Invention

[0004] Object of the Invention

[0005] To solve the problems existing in the traditional powder electrode in the above-mentioned prior art and the poor intrinsic hydrogen evolution activity, the present invention provides a preparation method and application of a hierarchical structure NiO x / CoP self-supporting electrode. A simple, low-cost, pollution-free, and easily scalable electrochemical method is used to construct a novel hierarchical structure electrode to improve the problems existing in the traditional powder electrode. At the same time, NiO x is compounded with CoP to improve the intrinsic hydrogen evolution activity of the electrode material.

[0006] Technical Solution

[0007] A preparation method of a hierarchical structure NiO x / CoP self-supporting electrode, comprising the following steps:

[0008] The first step: Prepare highly conductive nickel foam: Before electrochemical deposition, clean the nickel foam substrate with HCl, and then clean it with acetone, water, and ethanol respectively. Next, place it in a vacuum drying oven for drying;

[0009] The second step: Prepare NiO x nanotube arrays: Use a three-electrode system for electrochemical deposition. Take the highly conductive nickel foam prepared in the first step as the working electrode, Ag / AgCl as the reference electrode, and a carbon rod as the counter electrode. Deposit the Ni-Cu matrix alloy by pulsed electrochemical deposition, and then in-situ oxidize the obtained matrix alloy to obtain NiO x nanotube arrays. Next, wash them with water and ethanol respectively, and then place them in a vacuum drying oven for drying;

[0010] Step 3: Preparation of hierarchical NiO x / CoP self-supporting electrode: Electrochemical deposition was carried out using a three-electrode system. The NiO x nanotube array prepared in the second step was used as the working electrode, Ag / AgCl as the reference electrode, and a carbon rod as the counter electrode. CoP nanosheets were deposited by potentiostatic electrochemical deposition. Then, the prepared electrodes were washed with water and ethanol respectively, and finally dried in a vacuum drying oven.

[0011] As a further description of the above scheme, in the first step, the second step and the third step, the drying temperature of the vacuum drying oven is 60~80 °C, and the drying time is 6~12 h.

[0012] As a further description of the above scheme, in the first step, the second step and the third step, the number of washing times is 3~5 times.

[0013] As a further description of the above scheme, the prepared hierarchical NiO x / CoP self-supporting electrode is a hierarchical structure integrating NiO x nanotube array and CoP nanosheets, and the material is NiO x with multiple catalytic active centers and CoP.

[0014] As a further description of the above scheme, in the third step, in the hierarchical NiO x / CoP self-supporting electrode, the tube diameter of NiO x is 53~113 nm, and the thickness of CoP nanosheets is 3~5 nm.

[0015] As a further description of the above scheme, in the second step, when depositing the Ni-Cu parent phase alloy by pulse electrochemical deposition, the pulse high potential is -0.5~-0.9 V, the pulse low potential is -1.5~-1.0 V, the potential sweep rate is 0.1~1 mVs -1 , the pulse width is 0.1~5 s, and the electrolyte is a mixed solution of 1~100 mmol / L NiSO4∙6H2O, 1~50 mmol / L CuSO4∙5H2O and 1~100 mmol / L H3BO3.

[0016] As a further description of the above scheme, in the second step, the parent phase alloy is in-situ oxidized at a potential of 0.8~1.5 V for 5~1000 s.

[0017] As a further description of the above scheme, in the third step, when depositing CoP nanosheets by potentiostatic electrochemical deposition, the applied potentiostatic potential is -0.6~-1.5 V vs. Ag / AgCl, the electrolyte is a mixed solution of 1 - 200 mmol / L CoSO4∙7H2O, 1 - 200 mmol / L NaAc∙3H2O, 1 - 100 mmol / L Na3C6H5O7∙2H2O and 0.1 - 1 mol / L H2PO2∙H2O, and the deposition time is 300 - 3000 s.

[0018] As a further description of the above solution, in the first step, before electrochemical deposition, the nickel foam substrate is treated with 50 ml of 1 - 12 mol / L HCl for 5 - 60 min, and the size of the nickel foam is 1 cm × 2 cm.

[0019] A hierarchical structure NiO x / CoP self - supported electrode prepared by the above - mentioned preparation method x The application method of the / CoP self - supported electrode is to use the hierarchical structure NiO

[0020] Advantages and effects

[0021] Compared with the traditional preparation method, the electrochemical synthesis method adopted in this application has the characteristics of simplicity, low cost, pollution - free and scalability, and the prepared hierarchical structure NiO x / CoP self - supported electrode has a unique structure and morphology, that is, it integrates NiO x nanotube arrays and CoP nanosheet structures; compared with the traditional strategy of increasing the number of catalytic active sites, the hierarchical structure NiO x / CoP electrode material prepared in this application has multiple catalytic active centers, including water dissociation, hydrogen adsorption - desorption and hydroxyl transport; the hierarchical structure NiO x / CoP electrode shows significantly enhanced alkaline hydrogen evolution catalytic performance compared with traditional electrodes. In 1 mol / L KOH electrolyte, overpotentials of only 51 mV and 164 mV are required respectively to reach 10 mA cm -2 and 500 mA cm -2 current density. Description of the drawings

[0022] The present invention will be further described below in conjunction with the drawings and specific embodiments. The protection scope of the present invention is not limited only to the expressions of the following content.

[0023] Figure 1 The electrocatalytic HER performance of the NiO x nanotube arrays, CoP nanosheets and hierarchical structure NiO x / CoP prepared in Example 1 of the present invention.

[0024] Figure 2 SEM micrograph at low magnification of the Ni-Cu alloy in Example 1 of the present invention.

[0025] Figure 3 SEM micrograph at high magnification of the Ni-Cu alloy prepared in Example 1 of the present invention.

[0026] Figure 4 NiO prepared in Example 1 of the present invention x SEM micrograph at low magnification of the nanotube array.

[0027] Figure 5 NiO prepared in Example 1 of the present invention x SEM micrograph at high magnification of the nanotube array.

[0028] Figure 6 NiO prepared in Example 1 of the present invention x Nanotube array of NiO, CoP nanosheets and hierarchical structure NiO x X-ray diffraction (XRD) pattern of the / CoP electrode.

[0029] Figure 7 Hierarchical structure NiO prepared in Example 1 of the present invention x N2 adsorption-desorption isotherm of the / CoP.

[0030] Figure 8 Hierarchical structure NiO prepared in Example 1 of the present invention x Pore size distribution curve of the / CoP.

[0031] Figure 9 Hierarchical structure NiO prepared in Example 1 of the present invention x SEM micrograph of the / CoP.

[0032] Figure 10 Hierarchical structure NiO prepared in Example 1 of the present invention x Transmission electron microscope (TEM) micrograph of the / CoP.

[0033] Figure 11 Hierarchical structure NiO prepared in Example 1 of the present invention x High-resolution TEM micrograph of the / CoP.

[0034] Figure 12 Hierarchical structure NiO prepared in Example 1 of the present invention x Survey spectrum of X-ray photoelectron spectroscopy (XPS) of the / CoP electrode.

[0035] Figure 13 Hierarchical structure NiO prepared in Example 1 of the present inventionx High-resolution C 1s XPS spectrum of the / CoP electrode.

[0036] Figure 14 The hierarchical NiO prepared in Example 1 of the present invention x High-resolution Co 2p XPS spectrum of the / CoP electrode.

[0037] Figure 15 The hierarchical NiO prepared in Example 1 of the present invention x High-resolution P 2p XPS spectrum of the / CoP electrode.

[0038] Figure 16 The hierarchical NiO prepared in Example 1 of the present invention x High-resolution O 1s XPS spectrum of the / CoP electrode.

[0039] Figure 17 The hierarchical NiO prepared in Example 1 of the present invention x High-resolution Ni 2p XPS spectrum of the / CoP electrode.

[0040] Figure 18 The NiO prepared in Example 1 of the present invention x Nanotube arrays, CoP nanosheets and hierarchical NiO x Tafel curves of the / CoP electrode in 1 M KOH solution.

[0041] Figure 19 The hierarchical NiO prepared in Example 1 of the present invention x Actual H2 production and related Faraday efficiency of the / CoP electrode.

[0042] Figure 20 The NiO prepared in Example 1 of the present invention x Nanotube arrays, CoP nanosheets and hierarchical NiO x Electrochemical impedance curves of the / CoP electrode in 1 M KOH solution.

[0043] Figure 21 The hierarchical NiO prepared in Example 1 of the present invention x Multi-step chronopotentiometry curves of the / CoP electrode in 1 M KOH solution.

[0044] Figure 22 The hierarchical NiO prepared in Example 1 of the present invention x Chronoamperometry curves of the / CoP electrode in 1 M KOH solution. Detailed implementation manners Example 1

[0045] AsFigures 1 - 22 As shown in the figure, the following further describes Embodiment 1 of the present invention in conjunction with the accompanying drawings:

[0046] The hierarchical structure NiO x / CoP self-supporting electrode preparation method includes the following steps:

[0047] The first step: Prepare highly conductive nickel foam: Before electrochemical deposition, the nickel foam substrate is treated with HCl, and then washed with acetone, water, and ethanol respectively. Next, it is placed in a vacuum drying oven for drying; the use of HCl, acetone, water, and ethanol to treat the nickel foam substrate can remove surface organic contaminants and oxide layers, promote the transfer of charge from the NF substrate to the catalytic active sites, and improve the catalytic performance of the entire electrode.

[0048] The second step: Prepare NiO x nanotube arrays: Electrochemical deposition is carried out using a three-electrode system. The highly conductive nickel foam obtained in the first step is used as the working electrode, Ag / AgCl as the reference electrode, and a carbon rod as the counter electrode. Pulse electrochemical deposition is used to deposit the Ni-Cu parent alloy, and then the obtained parent alloy is in-situ oxidized to obtain NiO x nanotube arrays. Next, they are washed with water and ethanol respectively, and then placed in a vacuum drying oven for drying;

[0049] The third step: Prepare the hierarchical structure NiO x / CoP self-supporting electrode: Electrochemical deposition is carried out using a three-electrode system. The NiO x nanotube arrays obtained in the second step are used as the working electrode, Ag / AgCl as the reference electrode, and a carbon rod as the counter electrode. Constant potential electrochemical deposition is used to deposit CoP nanosheets, and then the prepared electrodes are washed with water and ethanol respectively, and finally placed in a vacuum drying oven for drying.

[0050] In the first step, second step, and third step of Embodiment 1 of the present invention, the drying temperature of the vacuum drying oven is 60 °C, and the drying time is 12 h. If outside these drying parameters, the surface of the sample is prone to oxidation at too high a temperature, and the drying effect cannot be achieved at too low a temperature, and it takes a long time.

[0051] In the first step, second step, and third step of Embodiment 1 of the present invention, the number of washing times is 3 times for each.

[0052] The hierarchical structure NiO x / CoP self-supporting electrode prepared in Embodiment 1 of the present invention is a hierarchical structure integrating NiO x nanotube arrays and CoP nanosheets, and the materials are NiO x with multiple catalytic active centers and CoP.

[0053] In the third step of Example 1 of the present invention, NiO in the hierarchical structure x in the NiO x / CoP self-supporting electrode has a tube diameter of 53 - 113 nm, and the thickness of the CoP nanosheets is 3 - 5 nm.

[0054] In the second step of Example 1 of the present invention, when depositing the Ni-Cu matrix alloy by pulsed electrochemical deposition, the pulsed high potential is -0.9 V, the pulsed low potential is -1.1 V, the potential sweep rate is 0.25 mV s -1 , the pulse width is 0.2 s, and the electrolyte is a mixed solution of 50 mmol / L NiSO4∙6H2O, 5 mmol / L CuSO4∙5H2O and 50 mmol / L H3BO3.

[0055] In the second step of Example 1 of the present invention, the matrix alloy is in-situ oxidized at a potential of 1.0 V for 350 s. Through in-situ electrochemical oxidation, not only can the amount of oxidation be precisely controlled, but also the internal resistance at the interface of the electrode system can be reduced, thereby accelerating the electron transfer kinetics.

[0056] In the third step of Example 1 of the present invention, when depositing CoP nanosheets by potentiostatic electrochemical deposition, the applied potentiostatic potential is -0.95 V vs . Ag / AgCl, the electrolyte is a mixed solution of 20 mmol / L CoSO4∙7H2O, 40 mmol / L NaAc∙3H2O, 10 mmol / L Na3C6H5O7∙2H2O and 0.25 mol / L H2PO2∙H2O, and the deposition time is 1000 s. The concentration of this Na3C6H5O7∙2H2O can regulate the morphology and microstructure of the deposit during the electrochemical deposition process, thereby preparing a catalyst with fully exposed active sites.

[0057] In the first step of Example 1 of the present invention, before electrochemical deposition, the nickel foam substrate is treated with 50 ml of 5 mol / L HCl for 20 min, and the size of the nickel foam is 1 cm × 2 cm.

[0058] Now, the specific content and implementation manner of the present invention will be further described in combination with the examples. However, the examples are only provided for illustration and cannot constitute a limitation to the technical solution of the present invention. Examples 2 and 3 of the present invention are similar to Example 1 in content. Now, Example 1 will be described in detail.

[0059] Characterization of the structure and morphology of the self-supporting electrode:

[0060] XRD, SEM and TEM were used to analyze the structure and morphology of the intermediate product in the step of the hierarchical structure NiO x / CoP electrode. AsFigure 2 and 3 As shown, Ni-Cu alloy nanoparticles with diameters ranging from dozens to hundreds of nanometers grow on nickel foam. After dealloying (as shown in Figure 4 and 5 ), a large number of nickel metal (NiO x ) nanotube arrays with surface oxidation and diameters of 53 - 113 nm are obtained. After electrochemically depositing CoP nanosheets on the surface of the NiO x nanotube arrays, a hierarchical structure NiO x / CoP self-supporting electrode is obtained. Figure 6 XRD patterns of NiO x nanotube arrays, CoP nanosheets, and hierarchical structure NiO x / CoP are shown. The diffraction peaks of CoP nanosheets and hierarchical structure NiO x / CoP correspond to orthorhombic CoP (ICSD No.290497); it is worth noting that no characteristic peaks of NiO x are detected, which is probably due to the formation of an amorphous structure. As shown in Figure 7 , the BET surface area of the hierarchical structure NiO x / CoP is 14 m 2 g -1 . Figure 8 The pore size distribution curve of x shows that mesopores exist in the hierarchical structure NiO x / CoP, and the center of the pore size is located at 2.2 nm. These mesopores are beneficial to the penetration of the electrolyte and the diffusion of gas during the catalytic process. From the microscopic electron microscope photos of the hierarchical structure NiO Figure 9 and 10 , it can be seen that CoP presents a morphology of ultrathin nanosheets. It is worth noting that the NiO x nanotube arrays with high conductivity are in direct contact with CoP nanosheets, which is beneficial to the transfer of electrons during the catalytic process. Figure 11 High-resolution TEM images of the hierarchical structure NiO x / CoP are shown. It can be found that there are 9 - 14 layers of CoP, which further confirms that CoP presents a morphology of ultrathin nanosheets. This ultrathin structure can expose more catalytic active sites. Next, XPS was used to study the surface composition and chemical state of the hierarchical structure NiO x / CoP electrode. Figure 12 XPS full spectra of the electrode are shown. Signals of Co, P, Ni, O, and C elements can be detected. The presence of C( Figure 13 ) is due to inevitable carbon contamination when the electrode is exposed to air. Figure 14is the high-resolution XPS spectrum of Co 2p. The two relatively sharp peaks located at 792.7 and 777.8 eV are the peaks of Co-P; while the four peaks and satellite peaks located at 798.2, 795.6, 781.6, and 779.4 eV are the peaks of cobalt oxides, which is caused by the surface oxidation of the sample exposed to air. In the XPS spectrum of the P 2p region ( Figure 15 ), the two peaks located at 129.2 and 130.7 eV are the peaks of P in phosphides, while the peak at 133.3 eV is the peak of P-O. For the XPS spectrum of O 1s ( Figure 16 ), the peaks with binding energies located at 531.3 and 529.7 eV correspond to metal-oxygen bonding (M-O) and oxygen in the lattice (O 2- ) bonding respectively. In the high-resolution XPS spectrum of Ni 2p ( Figure 17 ), according to the two main peaks and a group of satellite peaks at 871.1, 868.5, 855.8, and 852.4 eV, the formation of NiO x can be known.

[0061] At room temperature, the electrochemical performance characterization of the self-supporting electrode:

[0062] The electrochemical experiment was carried out using a standard three-electrode test system. As Figure 1 shown, the overpotential of the hierarchical structure NiO x / CoP electrode at a current density of 10 mA cm -2 is only 51 mV, lower than 275 mV of NiO x nanotube arrays and 123 mV of CoP nanosheets; in addition, the hierarchical structure NiO x / CoP electrode only needs an overpotential of 164 mV to reach a current density of 500 mA cm -2 , which indicates that the hierarchical structure NiO x / CoP electrode has excellent catalytic activity. Figure 18 is the Tafel curve. The Tafel slopes of NiO x nanotube arrays, CoP nanosheets, and hierarchical structure NiO x / CoP are 95, 79, and 56 mV dec −1 respectively. The smaller Tafel slope indicates that the hierarchical structure NiO x / CoP has faster HER catalytic reaction kinetics. In addition, according to the results detected by gas chromatography, the H2 production of the hierarchical structure NiO x / CoP is basically consistent with the theoretical value, and the Faraday efficiency is as high as 96% ( Figure 19) also further confirmed its high HER electrocatalytic activity. To study the charge transfer kinetics at the electrode / electrolyte interface during the HER process, an AC impedance test was carried out. As Figure 20 shown, the charge transfer resistance of the hierarchical structure NiO x / CoP is only 3.7 Ω, lower than that of NiO x nanotube arrays (328.0 Ω) and CoP nanosheets / CFP (76.1 Ω), indicating its faster charge transfer kinetics. To study the mass transfer characteristics and durability of the hierarchical structure NiO x / CoP electrode, multi-step chronopotentiometry and chronoamperometry tests were carried out. Figure 21 is the multi-step chronopotentiometry curve of the hierarchical structure NiO x / CoP electrode. The current density increased in 17 steps from 50 mA cm -2 to 800 mA cm -2 , and then returned to 50 mA cm -2 , and the corresponding potential changes during this process were recorded. In the first step, i.e., at 50 mA cm -2 , the potential immediately stabilized at -0.103 V vs. RHE (without iR compensation), and then remained constant within the remaining 500 s. Similar phenomena were also observed in the potential changes in the remaining steps. This chronopotentiometry behavior indicates that the hierarchical structure NiO x / CoP electrode has fast ion migration and gas diffusion capabilities. In addition, the hierarchical structure NiO x / CoP electrode was continuously electrolyzed at -0.051 V vs. RHE for 50 h, and the current hardly showed any obvious decay ( Figure 22 ), indicating that the hierarchical structure NiO x / CoP electrode has excellent stability. Example 2

[0063] The preparation method of the hierarchical structure NiO x / CoP self-supporting electrode of the second embodiment of the present invention includes the following steps:

[0064] The first step: Prepare highly conductive nickel foam: Before electrochemical deposition, the nickel foam substrate was treated with HCl, and then washed with acetone, water, and ethanol respectively. Next, it was placed in a vacuum drying oven for drying;

[0065] The second step: Prepare NiO xNanotube array: Electrochemical deposition was carried out using a three-electrode system. The highly conductive nickel foam obtained in the first step was used as the working electrode, Ag / AgCl as the reference electrode, and a carbon rod as the counter electrode. Pulse electrochemical deposition was used to deposit the Ni-Cu parent phase alloy, and then the obtained parent phase alloy was in-situ oxidized to obtain NiO x The nanotube array was then washed with water and ethanol respectively, and then dried in a vacuum drying oven;

[0066] Step 3: Preparation of hierarchical structure NiO x / CoP self-supporting electrode: Electrochemical deposition was carried out using a three-electrode system. The NiO x nanotube array obtained in the second step was used as the working electrode, Ag / AgCl as the reference electrode, and a carbon rod as the counter electrode. Constant potential electrochemical deposition was used to deposit CoP nanosheets, and then the prepared electrode was washed with water and ethanol respectively, and finally dried in a vacuum drying oven.

[0067] As a further description of the above scheme, in the first step, the second step and the third step, the drying temperature of the vacuum drying oven is 60 °C and the drying time is 6 h.

[0068] As a further description of the above scheme, in the first step, the second step and the third step, the number of washing times is 3 times.

[0069] As a further description of the above scheme, the prepared hierarchical structure NiO x / CoP self-supporting electrode is a hierarchical structure integrating NiO x nanotube array and CoP nanosheets, and the material is NiO with multiple catalytic active centers x and CoP.

[0070] As a further description of the above scheme, in the third step, in the hierarchical structure NiO x / CoP self-supporting electrode, NiO x is in the shape of a nanotube, and CoP is a nanosheet structure.

[0071] As a further description of the above scheme, in the second step, when depositing the Ni-Cu parent phase alloy by pulse electrochemical deposition, the pulse high potential is -0.5 V, the pulse low potential is -1.5 V, the potential sweep rate is 0.1 mV s -1 , the pulse width is 0.1 s, and the electrolyte is a mixed solution of 1 mmol / L NiSO4∙6H2O, 1 mmol / L CuSO4∙5H2O and 1 mmol / L H3BO3.

[0072] As a further description of the above scheme, in the second step, the parent phase alloy is in-situ oxidized at a potential of 0.8 V for 50 s.

[0073] As a further description of the above solution, in the third step, when depositing CoP nanosheets by potentiostatic electrochemical deposition, the applied potentiostatic potential is -0.6 V vs . Ag / AgCl, the electrolyte is a mixed solution of 1 mmol / L CoSO4∙7H2O, 1 mmol / L NaAc∙3H2O, 1 mmol / L Na3C6H5O7∙2H2O and 0.1 mol / L H2PO2∙H2O, and the deposition time is 300 s.

[0074] As a further description of the above solution, in the first step, before electrochemical deposition, the foam nickel substrate is treated with 50 ml of 1 mol / L HCl for 5 min, and the size of the foam nickel is 1 cm × 2 cm.

[0075] A hierarchical structure NiO prepared by the above preparation method x / CoP self-supporting electrode application method, the hierarchical structure NiO x / CoP self-supporting electrode is used as the hydrogen production reaction electrode, and rapid hydrogen production is achieved in 1 mol / L KOH electrolyte. Example 3

[0076] The preparation method of the hierarchical structure NiO x / CoP self-supporting electrode in Example 3 of the present invention includes the following steps:

[0077] The first step: Prepare highly conductive foam nickel: Before electrochemical deposition, the foam nickel substrate is treated with HCl, then washed with acetone, water and ethanol respectively, and then placed in a vacuum drying oven for drying;

[0078] The second step: Prepare NiO x nanotube arrays: Electrochemical deposition is carried out using a three-electrode system. The highly conductive foam nickel prepared in the first step is used as the working electrode, Ag / AgCl is used as the reference electrode, and a carbon rod is used as the counter electrode. Pulse electrochemical deposition is used to deposit the Ni-Cu parent alloy, and then the obtained parent alloy is in-situ oxidized to obtain NiO x nanotube arrays, then washed with water and ethanol respectively, and then placed in a vacuum drying oven for drying;

[0079] The third step: Prepare a hierarchical structure NiO x / CoP self-supporting electrode: Electrochemical deposition is carried out using a three-electrode system. Using the NiO prepared in the second step xUsing a nanotube array as the working electrode, Ag / AgCl as the reference electrode, and a carbon rod as the counter electrode, CoP nanosheets were deposited by potentiostatic electrochemical deposition. Then, the prepared electrodes were washed with water and ethanol respectively, and finally dried in a vacuum drying oven.

[0080] As a further description of the above scheme, in the first, second, and third steps, the drying temperature of the vacuum drying oven was 80 °C, and the drying time was 12 h.

[0081] As a further description of the above scheme, in the first, second, and third steps, the number of washing times was 5 times for each.

[0082] As a further description of the above scheme, the prepared hierarchical structure NiO x / CoP self-supporting electrode is a hierarchical structure integrating NiO x nanotube arrays and CoP nanosheets, and the materials are NiO x with multiple catalytic active centers and CoP.

[0083] As a further description of the above scheme, in the third step, in the hierarchical structure NiO x / CoP self-supporting electrode, NiO x has a nanotubular morphology, and CoP is a nanosheet structure.

[0084] As a further description of the above scheme, in the second step, when depositing the Ni-Cu parent phase alloy by pulse electrochemical deposition, the pulse high potential was -0.9 V, the pulse low potential was -1.0 V, the potential sweep rate was 1 mV s -1 , the pulse width was 5 s, and the electrolyte was a mixed solution of 100 mmol / L NiSO4∙6H2O, 50 mmol / L CuSO4∙5H2O, and 100 mmol / L H3BO3.

[0085] As a further description of the above scheme, in the second step, the parent phase alloy was in-situ oxidized at a potential of 0.8 - 1.5 V for 1000 s.

[0086] As a further description of the above scheme, in the third step, when depositing CoP nanosheets by potentiostatic electrochemical deposition, the applied potentiostatic potential was -1.5 V vs . Ag / AgCl, the electrolyte was a mixed solution of 200 mmol / L CoSO4∙7H2O, 200 mmol / L NaAc∙3H2O, 100 mmol / L Na3C6H5O7∙2H2O, and 1 mol / L H2PO2∙H2O, and the deposition time was 3000 s.

[0087] As a further description of the above solution, in the first step, before electrochemical deposition, the substrate of nickel foam is treated with 50 ml of 12 mol / L HCl for 60 min, and the size of the nickel foam is 1 cm × 2 cm.

[0088] A hierarchical structure NiO x / CoP self-supporting electrode application method, the hierarchical structure NiO x / CoP self-supporting electrode is used as a hydrogen evolution reaction electrode, and rapid hydrogen evolution can be achieved in 1 mol / L KOH electrolyte.

[0089] It is generally considered that hydrogen evolution overpotential less than 100 mV is rapid hydrogen evolution.

[0090] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the embodiments of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to enumerate all the embodiments here. All obvious changes or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. Preparation method of hierarchical structure NiO x / CoP self-supporting electrode, characterized in that: Including the following steps: The first step: Prepare highly conductive nickel foam: Before electrochemical deposition, the nickel foam substrate is treated with HCl, and then washed with acetone, water, and ethanol respectively. Next, it is placed in a vacuum drying oven for drying; Step 2: Preparation of NiO x Nanotube arrays: Electrochemical deposition was carried out using a three - electrode system. The highly conductive nickel foam obtained in the first step was used as the working electrode, Ag / AgCl as the reference electrode, and a carbon rod as the counter electrode. Pulse electrochemical deposition was used to deposit the Ni - Cu parent - phase alloy, and then the obtained parent - phase alloy was in - situ oxidized to obtain NiO x nanotube arrays. Next, they were washed with water and ethanol respectively, and then dried in a vacuum drying oven; Step 3: Preparation of hierarchical NiO x / CoP self-supporting electrode: Electrochemical deposition was carried out using a three-electrode system. The NiO x nanotube array obtained in the second step was used as the working electrode, Ag / AgCl as the reference electrode, and a carbon rod as the counter electrode. CoP nanosheets were deposited by potentiostatic electrochemical deposition. Then the prepared electrodes were washed with water and ethanol respectively, and finally dried in a vacuum drying oven.

2. Preparation method of hierarchical structure NiO x / CoP self-supporting electrode, characterized in that: In the first step, the second step, and the third step, the drying temperature of the vacuum drying oven is 60~80 °C, and the drying time is 6~12 h.

3. Preparation method of hierarchical structure NiO x / CoP self-supporting electrode, characterized in that: In the first step, the second step, and the third step, the number of washing times is 3~5 times.

4. Preparation method of hierarchical structure NiO x / CoP self-supporting electrode, characterized in that: The prepared hierarchical structure NiO x / CoP self-supporting electrode integrates the hierarchical structure of NiO x nanotube arrays and CoP nanosheets, and the materials are NiO x with multiple catalytic active centers and CoP.

5. Preparation method of hierarchical structure NiO x / CoP self-supporting electrode, characterized in that: In the third step, the NiO in the hierarchical structure x of the NiO x / CoP self-supporting electrode has a tube diameter of 53 to 113 nm, and the CoP nanosheets have a thickness of 3 to 5 nm.

6. Preparation method of hierarchical structure NiO x / CoP self-supporting electrode, characterized in that: In the second step, when depositing the Ni-Cu matrix alloy by pulse electrochemical deposition, the pulse high potential is -0.5~-0.9 V, the pulse low potential is -1.5~-1.0 V, the potential sweep rate is 0.1~1 mV s -1 , the pulse width is 0.1~5 s, and the electrolyte is a mixed solution of 1~100 mmol / L NiSO4∙6H2O, 1~50 mmol / L CuSO4∙5H2O and 1~100 mmol / L H3BO3.

7. Preparation method of hierarchical structure NiO x / CoP self-supporting electrode, characterized in that: In the second step, the parent phase alloy is in-situ oxidized at a potential of 0.8~1.5 V for 5~1000 s.

8. Preparation method of hierarchical structure NiO x / CoP self-supporting electrode, characterized in that: In the third step, when depositing CoP nanosheets by potentiostatic electrochemical deposition, the applied potentiostatic potential is -0.6~-1.5 V vs . Ag / AgCl, the electrolyte is a mixed solution of 1~200 mmol / L CoSO4∙7H2O, 1~200 mmol / L NaAc∙3H2O, 1~100 mmol / L Na3C6H5O7∙2H2O and 0.1~1 mol / L H2PO2∙H2O, and the deposition time is 300~3000 s.

9. Preparation method of hierarchical structure NiO x / CoP self-supporting electrode, characterized in that: In the first step, before electrochemical deposition, the nickel foam substrate is treated with 50 ml of 1~12 mol / L HCl for 5-60 min, and the size of the nickel foam is 1 cm × 2 cm.

10. Application method of a hierarchical structure NiO x / CoP self-supporting electrode, characterized in that: The hierarchical NiO x / CoP self-supporting electrode is used for the hydrogen evolution reaction electrode, and rapid hydrogen evolution can be achieved in 1 mol / L KOH electrolyte.

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