Preparation method and application of vanadium-based nickel-copper alloy composite electrode material

Abstract

The present invention discloses a preparation method and application of a vanadium-based nickel-copper alloy composite electrode material. The method includes: pretreating nickel foam; preparing a mixed solution according to the following concentrations: 7.5 - 15 mmol·L ‑1 CuSO4, 5 - 12.5 mmol·L ‑1 NaVO3, 0.25 - 1.0 mol·L ‑1 NiSO4, 0.3 - 0.9 mol·L ‑1 H3BO3; using the pretreated nickel foam as the working electrode and the prepared mixed solution as the electrolyte, and performing cyclic voltammetry electrodeposition with a potential window of -1.8 to -1.0 V, -2.1 to -1.0 V, or -2.4 to -1.0 V and a scanning speed of 2 - 12 mV·s ‑1 , to obtain a composite catalyst film, thereby obtaining the composite electrode material. The composite electrode material prepared by the present invention has extremely excellent catalytic kinetic characteristics and stability, high hydrogen evolution activity, and strong conductivity.

Description

Technical Field

[0001] The invention belongs to the technical field of composite electrode materials and relates to a preparation method and application of a vanadium-based nickel-copper alloy composite electrode material. Background Art

[0002] Hydrogen is a non-polluting, highly renewable energy source, so it is very attractive as an energy storage medium. Currently, water electrolysis is the most efficient and clean way to produce hydrogen, but the energy consumption of water electrolysis is too high. Therefore, the development of high-efficiency, high-activity and stable water electrolysis catalysts is a key factor in the pursuit of sustainable energy.

[0003] He et al. (XDHe, F.Xu, F.Li, L.Liu, Y.Wang, N.Deng, YWZhu, JBHe, Composition-performance relationship of NixCuy nanoalloys as hydrogen evolution electrocatalyst, J.Electroanal.Chem., 2017, 799, 235-241.) obtained nickel-copper alloys (Ni x Cu y ); because the surface structure lacks innovative design, it cannot expose enough catalytic active sites. Liang et al. (Y. Yue, K. Coburn, B. Reed, H. Liang, Hierarchical structured nickel-copper hybrids via simple electrodeposition, J. Appl. Electrochem., 2018, 48, 275-286.) 2+ / NH 4+A hierarchical Ni / Cu microporous coating was obtained on a copper substrate by one-step constant current deposition in a solution of ; Yu et al. (LP Yu, T. Lei, B. Nan, et al. Mo dopedporous Ni–Cu alloy as cathode for hydrogen evolution reaction in alkaline solution [J]. RSC Advances. 2015, 5 (100): 82078-82086) studied the electrocatalytic effect of Mo powder metallurgy doped three-dimensional porous Ni-Cu cathode in the hydrogen evolution reaction process. Although the composite of C, Mo, P and other materials has improved the catalytic performance of nickel-copper based materials to a certain extent, the limited intrinsic catalytic activity and conductivity of the base metal still limit the improvement space of its hydrogen evolution activity, and it is still far from enough to replace commercial Pt / C to meet industrial applications.

[0004] In the development of cathode materials for hydrogen production by electrolysis, many studies have been conducted on improving the catalytic performance of phosphides, sulfides, carbides, and hydroxides with the help of vanadium-based or vanadium oxide composites. However, due to the multi-valence properties of the vanadium element and the unclear mechanism of the dual synergistic hydrogen evolution effect of vanadium and copper on nickel, there have been no reports on the development of negative electrode materials using vanadium composite nickel-copper alloys. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a method for preparing a vanadium-based nickel-copper alloy composite electrode material, which has excellent catalytic kinetic characteristics and stability, high hydrogen evolution activity, enhanced material conductivity, and solves the problems existing in the prior art.

[0006] Another object of the present invention is to provide a vanadium-based nickel-copper alloy composite electrode material for use in electrolytic hydrogen production.

[0007] The technical solution adopted by the present invention is a method for preparing a vanadium-based nickel-copper alloy composite electrode material, comprising the following steps:

[0008] S1, pre-treating the nickel foam: cleaning and drying the nickel foam;

[0009] S2, prepare the mixed solution according to the following concentration: 7.5~15mmol·L -1 CuSO4, 5~12.5mmol·L - 1 NaVO3, 0.25~1.0mol·L -1 NiSO4, 0.3~0.9mol·L -1 H3BO3; using the pretreated nickel foam as the working electrode and the prepared mixed solution as the electrolyte, a composite catalyst film is obtained by cyclic voltammetry electrodeposition.

[0010] Furthermore, the step S1 is specifically as follows: ultrasonically clean the nickel foam in pure water and 95% ethanol solution for 10 to 30 minutes respectively, immerse it in anhydrous ethanol and seal it in a wide-mouth bottle after multiple cleanings, and pinch it with tweezers and place it on filter paper to dry naturally before use.

[0011] Furthermore, the composite catalyst film has a thickness of 10 to 20 μm.

[0012] Furthermore, in step S2, the potential window of cyclic voltammetry electrodeposition is -1.8 to -1.0 V, -2.1 to -1.0 V or -2.4 to -1.0 V, and the scanning speed is 2 to 12 mV·s -1 .

[0013] Furthermore, in step S2, the number of deposition cycles of cyclic voltammetry electrodeposition is 2 to 10.

[0014] Furthermore, the cyclic voltammetry electrodeposition is a three-electrode system, with a saturated calomel electrode as a reference electrode and a stone mill rod as a counter electrode.

[0015] Furthermore, the step S2 further comprises: after the electrodeposition is completed, washing the prepared catalyst with ultrapure water and anhydrous ethanol, and drying it naturally.

[0016] Furthermore, in step S1, the surface of the nickel foam is flat and smooth and the pore size is 100-300 μm.

[0017] Furthermore, the composite catalyst film obtained by electrodeposition in step S2 is formed by overlapping and stacking particles or block structures with a diameter of 200 to 500 nm.

[0018] Another technical solution adopted by the present invention is the application of the above-mentioned vanadium-based nickel-copper alloy composite electrode material in electrolytic hydrogen production.

[0019] The beneficial effects of the present invention are:

[0020] The embodiment of the present invention adopts cyclic voltammetry to prepare V-NiCu / NF electrode material. In the electrochemical performance test, the catalytic activity is excellent in alkaline medium (η 10 =29mV), and also exhibited excellent catalytic kinetics and stability. The three-dimensional network structure formed by the stacking of nanoparticles makes the electrocatalytic active area (ECSA) of V-NiCu / NF 46 times that of the empty nickel foam active area, providing a large number of active sites for the hydrogen evolution process and having excellent catalytic activity. Impedance analysis found that the composite of vanadium and nickel-copper alloy enhanced the conductivity of the material and exhibited excellent interface kinetics.

[0021] The embodiment of the present invention realizes the co-deposition of nickel, copper and vanadium on the surface of nickel foam by means of a transient redox process, so the plating solution formula and deposition parameters are the key to the present invention. The obtained V-NiCu / NF catalyst has a hydrogen evolution catalytic activity comparable to that of a commercial platinum-carbon catalyst, and also has outstanding catalytic stability, which can greatly save material costs in practical applications and has extremely high economic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1a 3 is the hydrogen evolution polarization curve of V-NiCu / NF at different NaVO3 concentrations in the embodiment of the present invention.

[0024] Figure 1b is the overpotential of V-NiCu / NF at different NaVO3 concentrations in the embodiments of the present invention.

[0025] Figure 2a 1 is the hydrogen evolution polarization curve of V-NiCu / NF at different scanning speeds in the embodiment of the present invention.

[0026] Figure 2b is the overpotential of V-NiCu / NF at different scanning speeds in the embodiment of the present invention.

[0027] Figure 3a 1 is the hydrogen evolution polarization curve of V-NiCu / NF under different deposition cycles in the embodiment of the present invention.

[0028] Figure 3b is the overpotential of V-NiCu / NF under different deposition cycles in the embodiment of the present invention.

[0029] Figure 4a 1 is the hydrogen evolution polarization curve of V-NiCu / NF under different potential windows in the embodiment of the present invention.

[0030] Figure 4b is the overpotential of V-NiCu / NF in different potential windows in the embodiment of the present invention.

[0031] Figure 5a It is the apparent morphology and structural characterization of the blank NF in the embodiment of the present invention.

[0032] Figure 5b This is the apparent morphology and structural characterization of V-NiCu / NF with a scale of 500 μm in the embodiment of the present invention.

[0033] Figure 5c This is the apparent morphology and structural characterization of V-NiCu / NF with a scale of 5 μm in the embodiment of the present invention.

[0034] Figure 5d This is the apparent morphology and structural characterization of V-NiCu / NF with a scale of 500nm in the embodiment of the present invention.

[0035] Figure 6a This is the scanning characterization area of ​​the V-NiCu / NF prepared in the embodiment of the present invention.

[0036] Figure 6b This is an EDX spectrum analysis diagram of V-NiCu / NF prepared in an embodiment of the present invention.

[0037] Figure 7 1 is an electron microscope image of V-NiCu / NF obtained in an embodiment of the present invention, wherein (a) is a high-angle annular dark field image, (b) is a nickel element distribution map during surface scanning, (c) is a copper element distribution map during surface scanning, (d) is an oxygen element distribution map during surface scanning, (e) is a vanadium element distribution map during surface scanning, and (f) is an overlay map of constituent elements.

[0038] Figure 8 2 are XPS spectra of Ni 2p (a), Cu 2p (b), V 2p (c), and O 1s (d) in the V-NiCu / NF prepared in the embodiment of the present invention.

[0039] Fig. 9 These are the test results of hydrogen evolution performance of the V-NiCu / NF electrode prepared in the embodiment of the present invention and other existing electrodes.

[0040] Fig.10 These are the test results of the electrocatalytic activity of the V-NiCu / NF electrode prepared in the embodiment of the present invention and the blank NF.

[0041] Fig.11a It is a Nyquist curve diagram of the V-NiCu / NF electrode prepared according to the embodiment of the present invention and other existing electrodes.

[0042] Fig.11b It is the Rct of the V-NiCu / NF electrode obtained in the embodiment of the present invention and other existing electrodes.

[0043] Fig.12a This is a multiple current step curve of the V-NiCu / NF electrode material obtained in an embodiment of the present invention.

[0044] Figure 12b It is the chronopotentiometry curve of the V-NiCu / NF electrode material prepared in the embodiment of the present invention.

[0045] Fig.13a This is the EDX spectrum analysis diagram of the product obtained in Comparative Example 1 of the present invention.

[0046] Fig.13b It is the hydrogen evolution polarization curve of the product obtained in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0047] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0048] Embodiment 1,

[0049] A method for preparing a vanadium-based nickel-copper alloy composite electrode material comprises the following steps:

[0050] S1, treatment of nickel foam; the cut nickel foam strips (length: 2 cm, thickness: 0.5 mm) were ultrasonically soaked in pure water prepared by Milli-Q and 95% ethanol solution for 10 to 30 minutes respectively, and then immersed in anhydrous ethanol and sealed in a wide-mouth bottle after multiple washings. Before use, gently pick it up with tweezers and place it on filter paper to dry naturally for subsequent use. The treatment of nickel foam is to remove surface oxides and surface oil stains, and at the same time increase the active sites on the surface of nickel foam, which can help the loading of the catalyst film and the presentation of the final catalytic performance.

[0051] S2, prepare 12.5mmol·L -1 CuSO4, 7.0mmol·L -1 NaVO3, 0.5 mol·L -1 NiSO4, 0.5 mol·L - 1 100mL of H3BO3 mixed solution, 50mL each time as electrolyte; CHI760E dual potentiostat as working platform, pretreated nickel foam as working electrode, saturated calomel electrode as reference electrode, stone mill rod as counter electrode. Set the potential window to (-2.1~-1.0)V, scan speed 5mV·s -1 , deposited 2 cycles, and electrodeposited the composite catalyst film in a three-electrode system using cyclic voltammetry (CV). After completion, the prepared catalyst was rinsed with ultrapure water and anhydrous ethanol and dried naturally to obtain the target catalyst V-NiCu / NF.

[0052] Changing the NaVO3 concentration can adjust the V content in V-NiCu / NF, thereby affecting its catalytic hydrogen evolution performance. When other conditions are constant, only the NaVO3 concentration is changed to prepare V-NiCu / NF electrode. -1 The NaVO3 concentration in KOH solution was 5.0 mmol·L -1 , 7.0mmol·L -1 、10.0mmol·L -1 、12.5mmol·L -1 (can also be expressed as mM) when the V-NiCu / NF electrode hydrogen evolution polarization curve is prepared, such as Figure 1a-1b shown.

[0053] Depend on Figure 1a It can be seen that the NaVO3 concentration is 5.0mmol·L -1 Increased to 12.5mmol·L -1 With the increase of concentration, the hydrogen evolution activity of V-NiCu / NF electrode did not show a gradual increase trend as expected, but at 7.0mmol·L -1 An inflection point appears at , and when the NaVO3 concentration increases further, the hydrogen evolution activity decreases instead. Figure 1b This is the variation law of hydrogen evolution overpotential of electrode materials prepared under different NaVO3 concentrations. Figure 1b It can be seen that when the NaVO3 concentration is 7.0mmol·L -1 , the current density is 10 mA cm -2 When the overpotential is 35mV and the current density is 100mA·cm -2 When the overpotential is 140 mV, the V-NiCu / NF electrode has the minimum hydrogen evolution overpotential. Therefore, the NaVO3 concentration prepared by the V-NiCu / NF composite electrode is 7.0 mmol·L -1 It is appropriate.

[0054] Other conditions were constant, only the NiSO4 concentration was changed (0.25, 0.5, 0.75, 1.0 mol·L -1 ) to prepare V-NiCu / NF electrode, and keep the electrolyte at 12.5mmol·L -1 CuSO4, 7.0mmol·L -1 NaVO3, 0.5 mol·L -1 The influence of H3BO3 on the hydrogen evolution performance of composite electrode materials is shown in Table 1:

[0055] Table 1 Effect of different concentrations of NiSO4 on hydrogen evolution performance of composite electrode materials

[0056] <![CDATA[NiSO4 concentration / mol·L -1 > 0.25 0.5 0.75 1.0 <![CDATA[Hydrogen evolution activity η of the composite electrode 10 / mV]]> 70 35 43 50

[0057] The results showed that the NiSO4 concentration was 0.5 mol·L -1 The obtained composite electrode exhibited excellent hydrogen evolution performance.

[0058] Other conditions were constant, only the concentration of CuSO4 was changed (7.5, 10.0, 12.5, 15.0 mmol·L -1 ) to prepare V-NiCu / NF electrode, and keep the electrolyte at 0.5 mol·L -1 NiSO4, 7.0mmol·L -1 NaVO3, 0.5 mol·L -1 The influence of H3BO3 on the hydrogen evolution performance of composite electrode materials is shown in Table 2:

[0059] Table 2 Effect of different concentrations of CuSO4 on hydrogen evolution performance of composite electrode materials

[0060] <![CDATA[CuSO4 concentration / mmol·L -1 > 7.5 10.0 12.5 15.0 <![CDATA[Hydrogen evolution activity η of the composite electrode 10 / mV]]> 61 39 35 44

[0061] The results showed that the concentration of CuSO4 was 12.5mmol·L -1 The obtained composite electrode exhibited excellent hydrogen evolution performance.

[0062] Other conditions were constant, only the H3BO3 concentration was changed (0.3, 0.5, 0.7, 0.9 mol·L -1 ) to prepare V-NiCu / NF electrode, and keep the electrolyte at 0.5 mol·L -1 NiSO4, 7.0mmol·L -1 NaVO3, 12.5mmol·L -1 The influence of CuSO4 on the hydrogen evolution performance of composite electrode materials is shown in Table 3:

[0063] Table 3 Effect of different concentrations of H3BO3 on the hydrogen evolution performance of composite electrode materials

[0064] <![CDATA[H3BO3 concentration / mol·L -1 > 0.3 0.5 0.7 0.9 <![CDATA[Hydrogen evolution activity η of the composite electrode 10 / mV]]> 61 35 75 89

[0065] The results showed that the concentration of H3BO3 was 0.5 mol·L -1 The obtained composite electrode exhibited excellent hydrogen evolution performance.

[0066] The composition and structure of the catalyst obtained in the embodiment of the present invention depend on the electrolyte formula (material types and concentration ranges of nickel, copper, and vanadium) of the early electrodeposition process and the key parameters of the deposition process (potential window of electrodeposition, scanning speed, and deposition number of turns, etc.), which require a lot of experimental exploration to obtain. In the present invention, the composition and concentration of the original material determine the elemental composition and molar ratio of the target catalyst, and directly determine the size of the synergistic promotion of the intrinsic hydrogen evolution activity of vanadium and copper elements on the nickel-based material. The process parameters of the electrodeposition process directly affect the physical phase, morphology, and microstructure of the target catalyst, determine the number of electrochemical active sites exposed by the catalyst in practical applications, and then determine its comprehensive catalytic performance and practical application value.

[0067] Embodiment 2,

[0068] During the electrochemical deposition process, the reaction scan rate also affects the hydrogen evolution performance of V-NiCu / NF electrocatalyst. In alkaline solution, the scan rate was 2mV·s -1 , 5mV·s -1 , 10mV·s -1 , 12mV·s -1 The remaining steps are the same as in Example 1 (NaVO3 concentration is 7.0 mmol·L -1 ), prepare the polarization curve of the electrocatalyst, such as Figure 2a-2b shown.

[0069] Depend on Figure 2a It can be seen that when the scanning speed is increased from 2mV·s -1 Increased to 12mV·s -1 When the scanning speed is increased to 10 mV·s -1 After that, the activity of hydrogen evolution reaction decreases and tends to be stable if the reaction temperature is continuously increased. Figure 2b The reaction scan rate was set to 5 mV·s -1 The V-NiCu / NF prepared by 10 =35mV,η 100 =118 mV). Therefore, the scanning speed should be selected as 5 mV·s when preparing the catalyst. -1 .

[0070] Embodiment 3,

[0071] The degree of metal loading on the surface of nickel foam is different when the number of deposition turns is different. The hydrogen evolution performance of V-NiCu / NF electrocatalysts prepared with different numbers of deposition turns is compared. Different numbers of deposition turns (Q) (1Q, 2Q, 4Q, 6Q, 8Q, 10Q) are measured in an alkaline environment, and the remaining steps are the same as in Example 1 (NaVO3 concentration is 7.0mmol·L-1 ), the prepared V-NiCu / NF electrode hydrogen evolution polarization curve and overpotential, such as Figure 3a-3b shown.

[0072] Depend on Figure 3a It can be seen that as the number of deposition cycles increases from 1Q to 10Q, the hydrogen evolution activity of the electrode shows an increasing trend. When the number of deposition cycles is 1-2Q, the hydrogen evolution activity is poor, and when it increases to 10Q, the hydrogen evolution activity is optimal. Therefore, the reaction activity of the electrocatalyst prepared when the deposition cycle is 10Q is the best. Figure 3b It can be seen that when the current density is 10 mA cm -2 The V-NiCu / NF prepared by depositing 10Q at 400 ℃ has the minimum hydrogen evolution overpotential (η 10 =19mV), but the reaction cycle is too long and is not recommended; while the V-NiCu / NF electrocatalyst prepared when depositing 8Q has a smaller hydrogen evolution overpotential (η 10 =29mV), and the reaction time is reasonable, so 8Q is selected as the deposition cycle of the composite electrode V-NiCu / NF.

[0073] Embodiment 4,

[0074] When other parameters are set the same, the relationship between hydrogen evolution performance and potential window range is explored. The range of the potential window will directly affect the degree of metal reduction on the surface of the material. In a solution with pH>7, the hydrogen evolution performance of the V-NiCu / NF electrode prepared with different potential window ranges is shown in Figure 2. Figure 4a-4b shown.

[0075] Three different reaction potential windows were selected: -1.8 to -1.0 V, -2.1 to -1.0 V, and -2.4 to -1.0 V. The remaining steps were the same as in Example 1 (NaVO3 concentration was 7.0 mmol·L -1 ). The more negative the potential window is, the longer the reduction time is. To save preparation time, the number of deposition cycles for the three potential windows is 4Q. Figure 4a It can be seen that the V-NiCu / NF electrocatalyst has good hydrogen evolution activity when the potential window is set to -2.1 to -1.0 V. Figure 2b The comparison shows that the hydrogen evolution overpotential of V-NiCu / NF catalyst is the smallest when the deposition potential window is -2.1~-1.0V (η 10 =42mV,η 100 =93mV), so the potential window is preferably -2.1 to -1.0V when preparing V-NiCu / NF electrode.

[0076] Embodiment 5,

[0077] Prepare 12.5mmol·L -1 CuSO4, 7.0mmol·L-1 NaVO3, 0.5 mol·L -1 NiSO4, 0.5 mol·L - 1 100mL of H3BO3 mixed solution, 50mL was transferred as electrolyte; CHI760E bipotentiostat was used as the working platform, pretreated nickel foam was used as the working electrode, saturated calomel electrode was used as the reference electrode, and stone mill rod was used as the counter electrode. The potential window was set to -2.1~-1.0V, and the scanning speed was 5mV·s -1 The deposition was 8 cycles, and the electrodeposition was carried out in a three-electrode system using cyclic voltammetry (CV). After washing three times with ultrapure water and anhydrous ethanol respectively, the target catalyst V-NiCu / NF was obtained after natural drying. Boric acid was used to regulate the pH value of the electrodeposition process to ensure the co-deposition of nickel-copper metal elements.

[0078] Figures 5a to 5d The structure and morphology of the prepared V-NiCu / NF at different magnifications, and blank nickel foam was used as a reference. Figure 5a As shown in the figure, the blank nickel foam presents a three-dimensional network structure of interwoven lotus flakes, with a smooth surface and a pore size of 100 to 300 μm. Figure 5b The V-NiCu / NF electrode prepared in Example 5 has the nickel-copper-vanadium alloy uniformly covering the surface of the nickel foam, and dendrites are precipitated in the surrounding edge area; Figure 5b Partially enlarged Figure 5c , 5d It can be observed that the center of the sample skeleton is formed by vertical accumulation of particles or block structures with a diameter of 200 to 500 nm, which are magnified and overlapped in particles, greatly increasing the surface area of ​​blank nickel foam, providing a large number of active sites for subsequent catalytic processes, enhancing the contact between the solid phase interface and the electrolyte liquid phase interface, and laying the foundation for its higher catalytic activity in the electrocatalytic process. The composite catalyst film of Example 5 has a thickness of 10 to 20 μm. The number of deposition turns, scanning speed and potential window of the catalyst preparation process will affect the deposition thickness of the film. If the deposition scanning speed is slow or the number of deposition turns is too large, the film thickness will increase. Too large a thickness will not only not increase the micro-nano structure of the catalyst and improve performance, but will form a porous structure in the early stage of the coating stacking blockage, and even increase the load of the surfactant, causing shedding, and affecting the stability of the catalytic material.

[0079] Embodiment 6,

[0080] In order to understand the distribution and composition of elements on the electrode surface, energy dispersive X-ray spectrometer (EDX) was used for characterization.

[0081] Prepare 12.5mmol·L -1 CuSO4, 7.0mmol·L-1 NaVO3, 0.5 mol·L -1 NiSO4, 0.5 mol·L - 1 100mL of H3BO3 mixed solution, 50mL was transferred as electrolyte; CHI760E bipotentiostat was used as the working platform, pretreated nickel foam was used as the working electrode, saturated calomel electrode was used as the reference electrode, and stone mill rod was used as the counter electrode. The potential window was set to -2.1~-1.0V, and the scanning speed was 5mV·s -1 , deposition was 8 cycles, electrodeposition was performed in a three-electrode system using cyclic voltammetry (CV), washed three times with ultrapure water and anhydrous ethanol respectively and then dried naturally to prepare two sets of V-NiCu / NF parallel samples; EDX test was performed, such as Figure 6a-6b shown.

[0082] Figure 6a For the selected pattern when using energy dispersive X-ray spectrometer (EDX), the corresponding analysis results are presented in Figure 6b . Figure 6b The elemental composition of the sample was described, and it was found that the sample was composed of four elements: Ni, Cu, V, and O. The elements contained were the same as those contained in the electrolyte solution configured during the preparation process. The atomic ratios of Ni, Cu, and V were 49.86%, 38.82%, and 6.65%, respectively. The content of oxygen element increased sharply along with the content of vanadium element. Since the sample contained vanadium oxide, vanadium oxide is unstable and easily oxidized, resulting in an increase in oxygen content. Figure 6b Here, At.No represents the atomic number of the constituent element, Mass[%] represents the mass fraction of the constituent element, and Atom[%] represents the atomic ratio of the constituent element.

[0083] The test results of Example 6 prove that the constituent elements of the composite electrode material of the present invention are Ni, Cu, V, and O, which preliminarily confirms the successful preparation of the composite material.

[0084] Embodiment 7,

[0085] The distribution of different elements on the surface of V-NiCu / NF electrode was characterized by Mapping analysis on the optimized catalyst.

[0086] Prepare 12.5mmol·L -1 CuSO4, 7.0mmol·L -1 NaVO3, 0.5 mol·L -1 NiSO4, 0.5 mol·L - 1100mL of H3BO3 mixed solution, 50mL was transferred as electrolyte; CHI760E bipotentiostat was used as the working platform, pretreated nickel foam was used as the working electrode, saturated calomel electrode was used as the reference electrode, and stone mill rod was used as the counter electrode. The potential window was set to -2.1~-1.0V, and the scanning speed was 5mV·s -1 , deposition is 8 cycles, and electrodeposition is carried out in a three-electrode system using cyclic voltammetry (CV). After washing three times with ultrapure water and anhydrous ethanol respectively, the target catalyst V-NiCu / NF is obtained by natural drying. In the surface scan distribution diagram, Figure 7 a is the high-angle annular dark field image of the sample, Figure 7 b~7e show the distribution maps of the four elements nickel, copper, oxygen and vanadium respectively. Figure 7 f is the superimposed distribution of the four elements on the electrode surface. It can be clearly observed from the figure that the O element is evenly distributed on the catalyst surface, Ni is brighter and Cu is darker, which means that Ni is distributed at the bottom of the porous sample, the distribution of Cu is consistent with the external structure, and the content of V is low and evenly distributed in the entire catalyst, indicating that the V-NiCu / NF electrocatalyst was successfully prepared.

[0087] Embodiment 8,

[0088] In order to obtain the existence form and valence state of the elements on the surface of V-NiCu / NF, the XPS spectrum of the electrode material was measured. -1 CuSO4, 7.0mmol·L -1 NaVO3, 0.5 mol·L -1 NiSO4, 0.5 mol·L -1 100mL of H3BO3 mixed solution, 50mL was transferred as electrolyte; CHI760E bipotentiostat was used as the working platform, pretreated nickel foam was used as the working electrode, saturated calomel electrode was used as the reference electrode, and stone mill rod was used as the counter electrode. The potential window was set to -2.1~-1.0V, and the scanning speed was 5mV·s -1 The deposition was 8 cycles, and the electrodeposition was carried out in a three-electrode system using cyclic voltammetry (CV). After washing three times with ultrapure water and anhydrous ethanol respectively and then naturally dried, the target catalyst V-NiCu / NF was obtained.

[0089] Figure 8 a~8d are the XPS spectra of the prepared V-NiCu / NF, from which the characteristic peaks of Ni 2p, Cu 2p, V 2p, and O1s can be clearly seen, indicating the presence of four elements, Ni, Cu, V, and O, on the surface of the material.

[0090] Figure 8a is the high-resolution XPS spectrum of Ni 2p. A pair of spin peak orbits appear at binding energies of 853.3 eV and 870.3 eV. According to the data comparison in the XPS library, they are Ni(0)2p 3 / 2 and 2p 1 / 2 orbit, indicating that the material contains metallic Ni. From the figure, we know that in addition to metallic Ni, nickel also exists in the form of Ni(II), and the corresponding accompanying peaks of Ni 2p appear at 862.0eV and 880.2eV.

[0091] Figure 8 From b, it can be seen that the material contains not only metallic Cu but also Cu(Ⅱ); Figure 8 The XPS spectrum of c has a spin-orbit peak of V2p 3 / 2 and 2p 1 / 2 , appear at 524.6eV and 517.2eV respectively. The data comparison in the XPS library is consistent with the position of the spin-orbit peak of V(Ⅲ), indicating that V is V 3+ exists in the form of; Figure 8 d is the high-resolution spectrum of oxygen element, from Figure 8 In d, we can see that the two emission peaks represent the bonding forms of two oxygen elements. The O1s with a binding energy of 531.6 eV belongs to hydroxyl oxygen, while the O corresponding to the other peak proves that in addition to hydroxyl oxygen, oxygen elements also exist in the form of oxygen ions. 3 / 2 The binding energy difference between them is 13.5 eV, which is consistent with the previously reported V 3+ The binding energy difference is close, indicating that vanadium and oxygen combine to form V2O3 covering the electrode surface.

[0092] Embodiment 9,

[0093] In order to explore the hydrogen evolution activity of V-NiCu / NF electrode, the loaded nickel foam was used as the research electrode, the platinum sheet electrode was used as the auxiliary electrode, and the reference electrode was a saturated calomel electrode. In alkaline electrolyte, the hydrogen evolution performance of four electrodes, blank NF (nickel foam), Ni / NF, NiCu / NF and V-NiCu / NF (prepared by the method of Example 5), was tested. The test curves were all compensated by 95% resistance. The results are shown in Figure 2. Fig. 9 shown.

[0094] Fig. 9 Figure (a) shows the polarization curves of different electrodes in alkaline solution. It can be seen that the overpotential of empty nickel foam is 10 mA cm -2The overpotential of hydrogen evolution in Ni / NF and NiCu / NF under the same conditions is 187mV and 157mV and 105mV respectively. The overpotential of V-NiCu / NF is only 35mV, which has excellent catalytic activity. The main reason is that metal vanadium has the ability to maximize the intrinsic activity of electrode materials. When metal vanadium is introduced into nickel-copper base as the cathode of hydrogen evolution reaction, the hydrogen evolution performance of the material is greatly improved. Since the hydrogen evolution reaction on the electrode is a complex process composed of many elementary processes, in order to analyze the control steps of the hydrogen process, compare the activation energy of different catalysts, and evaluate the performance of the cathode, the Tafel slope is used for analysis.

[0095] Fig. 9 Figure (b) shows the Tafel curves of different electrodes in alkaline solutions. For the V-NiCu / NF electrode, the hydrogen evolution reaction in an alkaline environment consists of double electron transfer. The detailed reaction mechanism in alkaline media is as follows: the first step is electrochemical adsorption (H2O+M+e - →MH ads +OH - ) Proton exchange occurs between vanadium and the electrolyte solution, producing adsorbed hydrogen ions (H * ); the second step is electrochemical desorption (MH ads +H2O+e - →H2, M represents metal vanadium), the adsorbed H * With H in water * Combined with H2, hydrogen is released from the catalyst surface. Therefore, the decisive factor affecting the hydrogen release ability of the catalyst is H * As can be seen from the figure, compared with NF, Ni / NF and NiCu / NF electrodes, the Tafel slope of the V-NiCu / NF electrode is the smallest, indicating that a large number of nanoparticles formed by the composite of vanadium and nickel-copper alloy in the embodiment of the present invention provide a large number of active sites for the hydrogen evolution reaction to adsorb more H * , indicating that the V-NiCu / NF electrode prepared in the embodiment of the present invention has good catalytic kinetic properties.

[0096] Embodiment 10,

[0097] In order to understand why the V-NiCu / NF catalyst (prepared by the method of Example 5) has a high catalytic activity, the double layer capacitance (C dl ), at 1.0 mol·L -1 The blank NF and V-NiCu / NF electrodes were characterized by cyclic voltammetry in KOH solution. Fig.10As shown, (a) is the CV curve of V-NiCu / NF, (b) is the double-layer capacitance diagram of V-NiCu / NF, (c) is the CV curve of blank NF, and (d) is the double-layer capacitance diagram of NF.

[0098] Depend on Fig.10 From Table 4, it can be found that the V-NiCu / NF electrode C measured at different scan rates dl 30.63mF·cm -2 , which is converted into an active area of ​​765.76 cm 2 Similarly, the active areas of NiCu / NF electrode and Ni / NF electrode are 56 cm 2 and 38cm 2 The active area of ​​blank nickel foam is 16.5 cm 2 . By comparison, it was found that the electrocatalytic active area of ​​the V-NiCu / NF electrode is 46 times that of the blank nickel foam. This shows that the granular protrusions formed by the vanadium-based porous composite expose a large number of active sites on the electrode surface. At the same time, the composite of metallic vanadium and metallic nickel and copper greatly improves the hydrogen evolution performance of the original nickel-copper alloy, effectively promoting the improvement of the intrinsic hydrogen evolution activity of nickel and copper materials. The three together create the ultra-high electrocatalytic activity of the target catalyst.

[0099] Table 4 shows the C of NiCu / NF, Ni / NF, NiCu / NF, and blank NF dl (electric double layer capacitance), ECSA (electrochemically active area) and Δn (increase factor) were used to further understand the changes in the active area of ​​the V-NiCu / NF electrode.

[0100] Table 4 C of different electrodes dl , ECSA and Δn

[0101]

[0102]

[0103] Embodiment 11,

[0104] The electrochemical impedance spectroscopy was used to measure the impedance spectra of four electrodes, namely, blank NF, Ni / NF, NiCu / NF and V-NiCu / NF (prepared by the method of Example 5), to find out the reason why the hydrogen evolution catalytic activity of the V-NiCu / NF electrode was enhanced. The test was carried out in an alkaline electrolyte solution, and the curve was fitted using Zsimpwin software. The test results are shown in FIG. Figures 11a-11b shown.

[0105] Fig.11aThe embedded equivalent circuit diagram was used to fit the Nyquist curves of four different electrodes: blank NF, Ni / NF, NiCu / NF and V-NiCu / NF. The diameter of the circle was used to evaluate the charge transfer potential Rct of the electrode in the hydrogen evolution reaction. Fig.11a It can be seen that the diameters of the semicircles corresponding to the four catalysts decrease in sequence, and the diameter of the semicircle corresponding to the V-NiCu / NF electrode is the smallest. Fig.11b It can be seen that the charge transfer resistance Rct of the V-NiCu / NF electrode is only 1.28Ω, which means that the conductivity of the electrode material is gradually improving, the resistance to electron transfer on the electrode surface is getting smaller and smaller, and the charge transfer rate is gradually accelerating. This shows that the composite of vanadium and nickel-copper alloy further promotes the charge transfer ability of the electrode surface, which is very beneficial to the catalytic process of the V-NiCu / NF electrode.

[0106] Embodiment 12,

[0107] In order to understand the stability of the V-NiCu / NF electrode material (prepared by the method of Example 5) in the catalytic process in an alkaline environment, the sample was characterized by using multiple current steps and chronoamperometry, as shown in FIG. Figure 12a-12b shown.

[0108] Fig.12a is the multi-current step curve of V-NiCu / NF electrode, Fig.12a The change of electrode potential over time at three different current densities is shown in the figure. The current density increases from 25 mA cm-1 to 35 mA cm-2 in 10 stages. -2 Gradually increase to 150mA·cm -2 Then increase to 300mA·cm -2 The potential value of the V-NiCu / NF electrode remained almost unchanged in the hydrogen evolution experiment, indicating that the rapid migration of charges in the solution increased the ability of the gas to escape quickly from the electrode surface, indicating that the catalyst showed good stability during the hydrogen evolution reaction.

[0109] Figure 12b The V-NiCu / NF electrode has a current density of 10 mA·cm -2 and 100mA·cm -2 The chronopotentiometry curve of Figure 12b It can be seen that at the beginning of the reaction, the hydrogen evolution potential increased because the catalyst needed to be activated briefly, and then stabilized after a period of time. The stability test lasted for 12 hours, and the corresponding potential fluctuation was only within 15mV, indicating that the catalyst performance was stable in the long-term catalytic reaction.

[0110] The embodiment of the present invention introduces vanadium into a nickel-copper alloy for the first time to develop an efficient hydrogen evolution cathode for electrolyzing water to produce hydrogen, develops a vanadium-based nickel-copper alloy with platinum-like hydrogen evolution activity, reduces the cost of producing water electrolysis equipment, improves water electrolysis technology, improves the competitiveness of the water electrolysis hydrogen evolution process, reduces equipment manufacturing costs, improves the performance of the hydrolysis method, and reduces energy consumption; obtains a universal preparation strategy for a new vanadium-based nickel-copper alloy hydrogen evolution catalyst, and provides a new idea for the development of new electrode materials.

[0111] The technical process of the present application is simpler, and a highly efficient vanadium-based nickel-copper alloy hydrogen evolution electrocatalyst is obtained by only one-step electrodeposition using cyclic voltammetry. The copper obtained by reduction in the present invention is not dissolved, thus truly realizing the composite of vanadium and nickel-copper alloy.

[0112] The reasons for the high hydrogen evolution activity of the catalyst prepared in the embodiment of the present invention mainly include three aspects: First, the introduction of Cu atoms can improve the adsorption performance of Ni atoms to active H atoms, thereby improving the intrinsic hydrogen evolution activity of the material. Second, the compounding of V promotes the formation of highly disordered metallic Ni, improves the adsorption of active hydrogen atoms and the desorption equilibrium of hydrogen molecules, thereby significantly improving the inherent hydrogen evolution activity. Third, the characteristics of the three-dimensional porous structure formed by the interweaving and interconnection of clusters formed by stacking nanoparticles bring a large number of catalytic active sites to the catalytic process, which greatly promotes the improvement of catalytic activity. The structural advantages of the target catalyst and the synergistic hydrogen evolution effect of NiCu alloy and VOx phase together create the outstanding catalytic performance of V-NiCu / NF.

[0113] The present invention directly realizes the dual composite of vanadium and the composition and structure of nickel-copper alloy by only one-step mild electrodeposition technology, so that the comprehensive catalytic performance (catalytic activity, stability and kinetic characteristics) of the catalyst are significantly improved, laying the foundation for replacing commercial precious metal catalysts in the industrial application of alkaline water electrolysis to produce hydrogen. Applying it to the field of electrolytic hydrogen production can not only greatly reduce the power consumption of electrolytic hydrogen production, but also promote its application process in industrial hydrogen production. At the same time, the development of vanadium-based high-end electrode materials not only extends the vanadium resource industry chain, but also realizes the effective connection between vanadium resources and the innovation chain of new energy characteristic industries, which is helpful to promote regional innovation-driven development.

[0114] The present invention uses a transient redox process (the process has strict requirements on the preparation parameters of potential window, scanning speed, and deposition cycles. It is based on this that the contents of Examples 2, 3, and 4 of the present invention are studied, because these preparation parameters directly determine the composition, microstructure, and crystal structure of the composite material, and thus directly affect the catalytic performance of the material) to achieve the co-deposition of nickel, copper, and vanadium on the surface of nickel foam.

[0115] Comparative Example 1: The electrochemical deposition method in Example 5 was replaced by a constant potential deposition method from a cyclic voltammetry method. The preparation parameters were: deposition potential -2.0 V, deposition time 600 s, and other parameters remained unchanged. The test results were as follows: Figure 13a-13b .

[0116] Although only the electrodeposition method was changed, the morphology and content of each component element of the prepared samples were completely different, and the performance of the V-NiCu / NF electrode prepared by constant potential deposition was significantly lower than that of the catalyst prepared by cyclic voltammetry in Example 5 (η CA =78mV significantly greater than η CV =35mV).

[0117] If only the vanadium source in Example 5 is replaced, NaVO3 is replaced with NH4VO3, the performance of the V-NiCu / NF electrode is compared with that of Example 5 as shown in Table 5:

[0118] Table 5 Comparison of hydrogen evolution activity of electrodes made from different vanadium sources

[0119]

[0120] By comparison, it was found that when the vanadium source NaVO3 was replaced with NH4VO3, the vanadium content of the prepared composite catalyst remained basically unchanged, the contents of nickel, copper and oxygen elements fluctuated slightly, and the hydrogen evolution performance of the catalyst only decreased by 7mV, which had no significant impact on the entire catalyst.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A method for preparing a vanadium-based nickel-copper alloy composite electrode material, characterized in that: The following steps are involved: S1, pre-treating the nickel foam: cleaning and drying the nickel foam; S2, prepare the mixed solution according to the following concentration: 7.5~15 mmol·L -1 CuSO4, 5~12.5 mmol·L -1 NaVO3, 0.25~1.0 mol·L -1 NiSO4, 0.3~0.9 mol·L -1 H3BO3; using the pretreated nickel foam as the working electrode and the prepared mixed solution as the electrolyte, a composite catalyst film is obtained by cyclic voltammetry electrodeposition; In step S2, the potential window of cyclic voltammetry electrodeposition is -2.1 to -1.0 V, and the scanning speed is 2 to 12 mV·s -1 ; In the step S2, the number of deposition cycles of cyclic voltammetry electrodeposition is 2 to 10; The composite catalyst film has a thickness of 10-20 μm; The composite catalyst film obtained by electrodeposition in S2 is composed of overlapping particles or block structures with a diameter of 200-500 nm.

2. The method for preparing a vanadium-based nickel-copper alloy composite electrode material according to claim 1, characterized in that: The step S1 specifically comprises: ultrasonically cleaning the nickel foam in pure water and 95% ethanol solution for 10 to 30 minutes respectively, sealing the nickel foam by immersion in anhydrous ethanol after multiple cleanings, and drying the nickel foam naturally before use.

3. The method for preparing a vanadium-based nickel-copper alloy composite electrode material according to claim 1, characterized in that: The cyclic voltammetry electrodeposition is a three-electrode system, with a saturated calomel electrode as a reference electrode and a graphite rod as a counter electrode.

4. The method for preparing a vanadium-based nickel-copper alloy composite electrode material according to claim 1, characterized in that: The step S2 further comprises: after the electrodeposition is completed, washing the prepared catalyst with ultrapure water and anhydrous ethanol, and drying it naturally.

5. The method for preparing a vanadium-based nickel-copper alloy composite electrode material according to claim 1, characterized in that: The surface of the nickel foam in S1 is flat and smooth and the pore size is 100-300 μm.

6. Use of a vanadium-based nickel-copper alloy composite electrode material obtained by the method for preparing a vanadium-based nickel-copper alloy composite electrode material as claimed in any one of claims 1 to 5 in electrolytic hydrogen production.

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