Chromium-nitrogen co-modified nickel tungstate full-pH hydrogen evolution electrode material, preparation method thereof and application of chromium-nitrogen co-modified nickel tungstate full-pH hydrogen evolution electrode material in seawater electrolysis hydrogen production

Abstract

The invention discloses a chromium-nitrogen co-modified nickel tungstate full-pH hydrogen evolution electrode material, a preparation method thereof and application of the chromium-nitrogen co-modified nickel tungstate full-pH hydrogen evolution electrode material in seawater electrolysis hydrogen production, the electrode material is obtained by taking foam iron or foam cobalt or foam nickel as a substrate material and synthesizing chromium-nitrogen co-modified nickel tungstate nanorods on the substrate material; the preparation method comprises the following steps: firstly, pretreating a substrate material, then carrying out hydrothermal reaction with nickel salt, tungstate and nitrate solution, then carrying out chromium and nitrogen modification, and finally obtaining the chromium-nitrogen co-modified full-pH hydrogen evolution electrode material. The preparation method is simple, only simple hydrothermal reaction and tubular furnace calcination are needed, the cost is low, the obtained full-pH water electrolysis hydrogen production electrode material has excellent seawater electrolysis hydrogen production activity and shows excellent performance in acidic, neutral and alkaline electrolytes, and the seawater electrolysis hydrogen production activity is greatly improved; a further research shows that the electrode material also has excellent stability of hydrogen production by full-pH seawater electrolysis, and is beneficial to large-scale hydrogen production by water electrolysis.

Description

Technical Field

[0001] The present invention relates to the technical field of seawater electrolysis catalysts, and in particular to a chromium-nitrogen co-modified nickel tungstate full-pH hydrogen evolution electrode material, a preparation method thereof, and an application thereof in seawater electrolysis for hydrogen production. Background Art

[0002] Faced with increasingly severe energy crises and environmental pollution, the development of clean, renewable energy and efficient energy storage and conversion technologies is crucial for the sustainable development of human society. Hydrogen, with its high energy density, green product quality, and wide range of applications, is widely considered a highly efficient carrier of next-generation clean energy. Hydrogen production via water electrolysis can convert unstable renewable energy into stable chemical energy, making electrocatalytic water splitting coupled with renewable energy utilization devices considered one of the most promising green energy utilization approaches. The water electrolysis reaction can generally be divided into two half-reactions: the cathodic hydrogen evolution reaction (HER) with two electrons and the anodic oxygen evolution reaction (OER) with four electrons. To ensure efficient water electrolysis, excellent electrocatalysts are essential to accelerate the sluggish kinetics and reduce the overpotentials of hydrogen and oxygen evolution. Currently, precious metal-based materials such as Pt are recognized as excellent electrocatalysts for the HER, but their limited availability and high cost severely limit their widespread application. On the other hand, the electrolytes used in water electrolysis for hydrogen production can be classified into acidic, neutral, and alkaline electrolytes depending on the application scenario. However, precious metals and currently studied catalysts cannot maintain long-term stable operation in acidic, neutral, and alkaline electrolytes. Therefore, the design and development of a stable, efficient, and low-cost hydrogen evolution catalyst across all pH ranges in acidic, neutral, and alkaline electrolytes is of great significance for the practical application of water electrolysis for hydrogen production.

[0003] In recent years, transition metal tungstate-based nanomaterials have become a research hotspot in electrochemistry due to their abundant reserves, low cost, corrosion resistance, and environmental friendliness. Transition metal tungstates (MWO4) can be divided into two structural types, determined by the radius of the divalent cation. MWO4 with small cations (e.g., M = Fe, Co, and Ni) typically exhibits a monoclinic wolframite structure, while those with large cations (e.g., M = Ca, Ba, and Sr) typically exhibit a tetragonal scheelite structure. Research has shown that these materials hold great potential for electrochemical applications such as supercapacitors, lithium-ion batteries, sodium-ion batteries, and electrochemical sensors. However, the design, preparation, and performance of tungstate catalysts for electrocatalytic water splitting to produce hydrogen are still in their infancy.

[0004] Although transition metal tungstate-based nanomaterials are abundant, inexpensive, and readily available, their catalytic performance is far from practical. Therefore, researchers have attempted to improve their catalytic performance by designing and adjusting the structure of tungstate materials. To date, researchers have used various methods, such as composites, to prepare tungstate nanostructured materials to enhance hydrogen evolution performance. However, the conventional alkaline hydrogen evolution activity of these catalysts remains significantly lower than that of the precious metal Pt, and the catalysts' hydrogen evolution activity is also very low across the entire pH range of acidic, neutral, and alkaline solutions. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem that existing catalysts cannot maintain long-term stable operation in acidic, neutral and alkaline electrolytes, and to provide a chromium-nitrogen co-modified nickel tungstate full pH hydrogen evolution electrode material and its preparation method and application in seawater electrolysis to produce hydrogen. The chromium-nitrogen co-modified nickel tungstate full pH hydrogen evolution electrode material of the present invention has excellent water electrolysis hydrogen production activity in acidic electrolytes, neutral electrolytes and alkaline electrolytes, and can electrolyze seawater to produce hydrogen stably for a long time in various electrolytes.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions: The invention discloses a chromium-nitrogen co-modified nickel tungstate full pH hydrogen evolution electrode material. The electrode material is based on foamed iron, foamed cobalt or foamed nickel and is obtained by synthesizing chromium-nitrogen co-modified nickel tungstate nanorods on the base material.

[0007] The chromium-nitrogen co-modified nickel tungstate nanorods of the present invention have a radius of 500-1800 nm and a length of 4-15 μm.

[0008] The Cr element in the electrode material of the present invention is 0.5%-5% of the total mass of Ni, W, N, and Cr, preferably 1.0%-3.5%.

[0009] The N element in the electrode material of the present invention is 0.5%-5% of the total mass of Ni, W, N and Cr, preferably 1.0%-3.5%.

[0010] The present invention also provides a method for preparing a chromium-nitrogen co-modified nickel tungstate full pH hydrogen evolution electrode material, comprising the following steps: (1) Pretreatment: Wet the surface of the substrate with anhydrous ethanol, let it dry naturally, then soak it in a dilute hydrochloric acid solution to remove surface impurities, then wash it with water and anhydrous ethanol in sequence, and dry it naturally before use; (2) Hydrothermal reaction: nickel salt, tungstate and nitrate are dissolved in deionized water to obtain a hydrothermal reaction solution, and then the pretreated substrate material is immersed in the hydrothermal reaction solution for hydrothermal reaction. After the reaction is completed, the product is taken out, rinsed with deionized water and naturally dried to obtain nickel tungstate hydrate (NOW); (3) Chromium modification: A certain concentration of chromium salt solution is used as the hydrothermal reaction solution, and the obtained nickel tungstate hydrate is immersed in the hydrothermal reaction solution for hydrothermal reaction. After the reaction is completed, the product is taken out, rinsed with deionized water, and then naturally dried to obtain Cr-modified nickel tungstate hydrate (Cr-NOW); (4) Nitrogen modification: In a tube furnace, urea was used as the N source, and Cr-modified nickel tungstate hydrate was used as the modified substance. The temperature was raised to 500 °C at a rate of 2 °C / min under nitrogen or Ar atmosphere and the reaction was kept at this temperature for 2 h. The nitrogen source was provided by the decomposition of urea, and then nitrogen modification was carried out on Cr-NOW by chemical vapor deposition to obtain chromium-nitrogen co-modified nickel tungstate full pH hydrogen evolution electrode material (CrN-NOW).

[0011] According to the above scheme, the nickel salt in step (2) is nickel chloride with a concentration of 0.01~0.09 mol / L; the tungstate is ammonium tungstate with a concentration of 0.001~0.009 mol / L; the nitrate is sodium nitrate with a concentration of 0.01~0.1 mol / L; the temperature of the hydrothermal reaction is 120~180℃, and the time is 1~15 h.

[0012] According to the above scheme, the chromium salt solution in step (3) is 0.001~0.015 mol / L.

[0013] According to the above scheme, the hydrothermal reaction temperature in step (3) is 90~180℃, and the reaction time is 1~9 hours.

[0014] According to the above scheme, the amount of urea used in step (4) is 0.1~1.9 g.

[0015] The present invention also provides an application of a chromium-nitrogen co-modified nickel tungstate full-pH hydrogen evolution electrode material in hydrogen production by electrolysis of seawater.

[0016] The present invention synthesizes nickel tungstate hydrate on a pretreated substrate material, and then performs Cr modification through secondary hydrothermal treatment, followed by N modification through urea treatment, thereby synthesizing a chromium-nitrogen co-modified nickel tungstate full pH hydrogen evolution electrode material. The nickel tungstate material itself not only has few catalytic sites, but also has poor intrinsic hydrogen evolution activity. The chromium-nitrogen co-modified nickel tungstate nanorod material designed by the present invention has a three-dimensional open structure and can provide a large number of catalytic sites for hydrogen evolution reaction. In order to solve the problem of low intrinsic hydrogen evolution activity in acidic, neutral and alkaline electrolytes, the present invention starts from the electronic structure of the bottom material, and simultaneously introduces a non-metallic N element with strong electronegativity and a metallic Cr element with rich valence to systematically optimize the electronic structure of the material, thereby obtaining a new catalyst suitable for hydrogen production by acidic, neutral and alkaline water electrolysis. Therefore, the chromium-nitrogen co-modified nickel tungstate nanorod electrode material has excellent hydrogen production activity by water electrolysis in all pH conditions.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) The chromium-nitrogen co-modified nickel tungstate nanorod electrode material (CrN-NOW) provided by the present invention uses Cr and N elements to optimize the material's electronic structure in multiple aspects, resulting in excellent water electrolysis hydrogen production activity and stability in acidic, neutral, and alkaline electrolytes, which is beneficial for large-scale water electrolysis hydrogen production. The full-pH water electrolysis hydrogen production catalyst has excellent seawater electrolysis hydrogen production activity, significantly enhanced seawater electrolysis hydrogen production activity, and excellent seawater hydrogen production stability.

[0018] (2) The chromium-nitrogen co-modified nickel tungstate nanorod electrode material of the present invention only requires a simple hydrothermal reaction and tubular furnace calcination method. The raw materials for preparation are cheap and easy to obtain, and the synthesis is simple, which is conducive to the development of key catalytic materials for hydrogen production by electrolysis of water and promotes the large-scale application of hydrogen production by electrolysis of seawater. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 XRD patterns of NOW and Cr-NOW materials synthesized in Comparative Examples 1 and 2; Figure 2 This is the XRD pattern of the CrN-NOW material synthesized in Example 3 of the present invention; Figure 3 This is the SEM image of the NOW material synthesized in Comparative Example 1; Figure 4 is a SEM image of the Cr-NOW material synthesized in Comparative Example 2; Figure 5 This is a scanning electron microscope image of the CrN-NOW electrode material synthesized in Example 3 of the present invention; Figure 6 TEM image of the CrN-NOW electrode material synthesized in Example 3 of the present invention; Figure 7This is an energy dispersive X-ray elemental map of the CrN-NOW electrode material synthesized in Example 3 of the present invention; Figure 8 This is an energy dispersive X-ray elemental line scan spectrum of the CrN-NOW electrode material synthesized in Example 3 of the present invention; Figure 9 Ni 2p high-resolution energy spectra of the NOW, Cr-NOW, and CrN-NOW electrode materials synthesized in Comparative Examples 1 and 2 and Example 3 of the present invention; Figure 10 W 4f high-resolution energy spectra of NOW, Cr-NOW, and CrN-NOW electrode materials synthesized in Comparative Examples 1 and 2 and Example 3 of the present invention; Figure 11 Cr 2p high-resolution energy spectra of Cr-NOW and CrN-NOW electrode materials synthesized in Comparative Example 2 and Example 3 of the present invention; Figure 12 This is the N 1s high-resolution energy spectrum of the CrN-NOW electrode material synthesized in Example 3 of the present invention; Figure 13 Polarization curves of hydrogen evolution in alkaline electrolyte (1 M KOH) for CrN-NOW1, CrN-NOW2, and CrN-NOW electrode materials prepared in Examples 1-3 of the present invention; Figure 14 The hydrogen evolution polarization curves of NOW, Cr-NOW, and CrN-NOW electrode materials prepared in Comparative Example 1, Comparative Example 2, and Example 3 in an alkaline electrolyte (1 M KOH) are shown; Figure 15 The hydrogen evolution polarization curves of NOW, Cr-NOW, and CrN-NOW electrode materials prepared in Comparative Example 1, Comparative Example 2, and Example 3 in an acidic electrolyte (0.5 M H2SO4); Figure 16 The hydrogen evolution polarization curves of NOW, Cr-NOW, and CrN-NOW electrode materials prepared in Comparative Example 1, Comparative Example 2, and Example 3 in a neutral electrolyte (1 M PBS) are shown; Figure 17 The CrN-NOW electrode material and other HER catalysts in Example 3 of the present invention output 10 mA / cm 2 Required overpotential diagram; Figure 18 Electrochemical double layer capacitors of NOW, Cr-NOW, and CrN-NOW electrode materials prepared in Comparative Example 1, Comparative Example 2, and Example 3; Figure 19The hydrogen evolution polarization curves of NOW, Cr-NOW, and CrN-NOW electrode materials prepared in Comparative Example 1, Comparative Example 2, and Example 3 are shown; Figure 20 The hydrogen evolution stability test diagram of the CrN-NOW electrode material prepared in Example 3 of the present invention in an alkaline electrolyte (constant current test 100 mA / cm 2 ); Figure 21 The hydrogen evolution stability test diagram of the CrN-NOW electrode material prepared in Example 3 of the present invention in an acidic electrolyte (constant current test 100 mA / cm 2 ); Figure 22 The hydrogen evolution stability test diagram of the CrN-NOW electrode material prepared in Example 3 of the present invention in a neutral electrolyte (constant current test 100 mA / cm 2 ). DETAILED DESCRIPTION

[0020] To facilitate understanding of the technical solutions of the present invention, the principles and features of the present invention will be described below in conjunction with specific embodiments. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0021] The substrate material used in the comparative examples and examples of the present invention is nickel foam with a purity of 99.9 wt%, a thickness of 0.15 cm, a size of 2x4 cm, a pore size of 100 ppi, a porosity of 98%, and an area density of 500 g / m 2 All drugs used were of analytical grade. Example 1

[0022] A method for preparing a chromium-nitrogen co-modified nickel tungstate hydrogen evolution electrode material of this embodiment includes the following steps: (1) Pretreatment: Wet the surface of nickel foam with anhydrous ethanol, let it dry naturally, and then soak it in dilute hydrochloric acid solution to remove impurities in the surface oxide layer. Then wash it with water and anhydrous ethanol in turn, and dry it naturally before use. (2) Hydrothermal reaction: Weigh 0.642 g of ammonium tungstate, 0.5 g of nickel chloride and 0.356 g of sodium nitrate and dissolve them in deionized water to obtain a hydrothermal reaction solution, wherein the concentration of ammonium tungstate is 0.0045 mol / L, the concentration of nickel chloride is 0.028 mol / L, and the concentration of sodium nitrate is 0.056 mol / L; then the pretreated metal nickel foam is placed vertically into the inner liner of the high-pressure reactor, and then the high-pressure reactor is placed in a constant temperature box, set the temperature at 160 °C and react at a constant temperature for 6 h. After the reaction is completed, wait for the constant temperature box to slowly cool to room temperature (about 30 °C), take out the product and rinse it with distilled water for about 5 minutes, and dry it naturally to obtain nickel tungstate hydrate (NOW); (3) Chromium modification: A 0.003 mol / L chromium nitrate solution was used as the secondary hydrothermal reaction solution, and the obtained nickel tungstate hydrate was immersed in the hydrothermal reaction solution. The hydrothermal reaction was carried out at 110 °C for 6 h. After the reaction was completed, the constant temperature box was slowly cooled to room temperature (about 30 °C), the product was taken out, rinsed with deionized water, and then naturally dried to obtain Cr-modified nickel tungstate hydrate (Cr-NOW); (4) Nitrogen modification: In a tube furnace, the dried Cr-NOW electrode material was placed in the middle of the tube furnace, 1.0 g of urea was weighed and placed in the upper air inlet, and the nitrogen source was provided by the decomposition of urea. The temperature was raised to 500 °C at a rate of 2 °C / min under nitrogen or Ar atmosphere and the reaction was carried out at a constant temperature for 2 h. After the reaction was completed, the constant temperature box was slowly cooled to room temperature to obtain chromium-nitrogen co-modified nickel tungstate full pH hydrogen evolution electrode material (CrN-NOW1). Example 2

[0023] The preparation method of a chromium-nitrogen co-modified nickel tungstate full-pH hydrogen evolution electrode material (CrN-NOW2) in this embodiment is similar to that in Example 1, except that a chromium nitrate salt solution with a concentration of 0.015 mol / L is used as the secondary hydrothermal reaction solution. Example 3

[0024] The preparation method of a chromium-nitrogen co-modified nickel tungstate full-pH hydrogen evolution electrode material (CrN-NOW) in this embodiment is similar to that in Example 1, except that a chromium nitrate salt solution with a concentration of 0.008 mol / L is used as the secondary hydrothermal reaction solution.

[0025] Comparative Example 1 A nickel tungstate hydrate (NOW) material in this comparative example is prepared as follows: (1) Wet the surface of nickel foam (4 cm × 2 cm) with anhydrous ethanol, let it dry naturally, and then soak it in dilute hydrochloric acid solution to remove impurities in the surface oxide layer. Then wash it with water and anhydrous ethanol in sequence, and dry it naturally before use. (2) Weigh 0.642 g of ammonium tungstate, 0.5 g of nickel chloride and 0.356 g of sodium nitrate and dissolve them in deionized water to obtain a hydrothermal reaction solution, wherein the concentration of ammonium tungstate is 0.0045 mol / L, the concentration of nickel chloride is 0.028 mol / L and the concentration of sodium nitrate is 0.056 mol / L; then vertically place the pretreated metal nickel foam into the inner liner of a high-pressure reactor, and then place the high-pressure reactor into a constant temperature box, set the temperature at 160 °C and react at this temperature for 6 h. After the reaction is completed, wait for the constant temperature box to slowly cool down to room temperature (about 30 °C), take out the product, rinse it with distilled water for about 5 min, and dry it naturally to obtain nickel tungstate hydrate (NOW).

[0026] Comparative Example 2 A Cr-modified nickel tungstate hydrate (Cr-NOW) material of this comparative example is prepared as follows: (1) Pretreatment: Wet the surface of nickel foam (NF) with anhydrous ethanol, let it dry naturally, and then soak it in a dilute hydrochloric acid solution to remove impurities in the surface oxide layer. Then wash it with water and anhydrous ethanol in turn, and dry it naturally before use. (2) Hydrothermal reaction: Weigh 0.642 g of ammonium tungstate, 0.5 g of nickel chloride and 0.356 g of sodium nitrate and dissolve them in deionized water to obtain a hydrothermal reaction solution, wherein the concentration of ammonium tungstate is 0.0045 mol / L, the concentration of nickel chloride is 0.028 mol / L, and the concentration of sodium nitrate is 0.056 mol / L; then the pretreated metal nickel foam is placed vertically into the inner liner of the high-pressure reactor, and then the high-pressure reactor is placed in a constant temperature box, set the temperature at 160 °C and react at a constant temperature for 6 h. After the reaction is completed, wait for the constant temperature box to slowly cool to room temperature (about 30 °C), take out the product and rinse it with distilled water for about 5 minutes, and dry it naturally to obtain nickel tungstate hydrate (NOW); (3) Chromium modification: A 0.003 mol / L chromium nitrate solution was used as the secondary hydrothermal reaction solution. The obtained nickel tungstate hydrate was immersed in the hydrothermal reaction solution and subjected to hydrothermal reaction at 110 °C for 6 h. After the reaction, the constant temperature box was slowly cooled to room temperature (about 30 °C). The product was taken out, rinsed with deionized water, and then naturally dried to obtain Cr-modified nickel tungstate hydrate (Cr-NOW).

[0027] The nickel tungstate hydrate (NOW) synthesized in Comparative Example 1 and the Cr-modified nickel tungstate hydrate (Cr-NOW) synthesized in Comparative Example 2 were subjected to XRD tests. Figure 1 As shown in the figure, it can be found that except for the diffraction peak of Ni (PDF#04-0850) from the substrate, the other diffraction peaks of the two materials synthesized in Comparative Examples 1 and 2 are consistent with those of the standard material Ni4W6O 21 The diffraction peaks of (OH)2·4H2O (PDF#47-0143) match those of NOW and Cr-NOW materials after the hydrothermal reaction, indicating that the crystal phase of NOW and Cr-NOW materials generated after the hydrothermal reaction is nickel tungstate hydrate material, and the modification of Cr does not produce a new phase.

[0028] Figure 2 The XRD pattern of the CrN-NOW material synthesized in Example 3 of the present invention reveals that, in addition to the diffraction peaks from the Ni (PDF#04-0850) in the substrate, the remaining diffraction peaks of the synthesized catalyst after tube furnace calcination and nitrogen treatment match those of the standard material NiWO4 (PDF#15-0755), indicating that the nitrogen-modified CrN-NOW material is nickel tungstate.

[0029] The NOW synthesized in Comparative Example 1 was subjected to electron microscope scanning. The results are as follows: Figure 3 As shown in the figure, scanning electron microscopy found that the surface of nickel foam became very rough after the hydrothermal reaction. Further observation revealed that NOW has a three-dimensional open structure of nanorods with a radius of 500~1800 nm and a length of nickel tungstate nanorods of 4~15 μm.

[0030] The Cr-NOW synthesized in Comparative Example 2 was subjected to electron microscope scanning. The results are as follows: Figure 4 As shown in the figure, scanning electron microscopy revealed that after Cr modification, Cr-NOW still has a three-dimensional open nanorod structure. This open nanorod structure increases the contact area between the catalyst and the electrolyte, which helps provide more catalytic active sites.

[0031] The CrN-NOW electrode material synthesized in Example 3 was subjected to electron microscope scanning, and the results were as follows: Figure 5 As shown in Figure 3, the CrN-NOW nanostructure was also well preserved after urea calcination, which indicates that CrN-NOW has a three-dimensional open nanorod structure.

[0032] Figure 6 High-resolution transmission electron microscopy results of the CrN-NOW electrode material synthesized in Example 3 of the present invention are shown. As shown in the figure, the red dashed box area of ​​the HRTEM image is magnified. As shown by the lattice fringes in the magnified HRTEM image on the right, the interplanar spacing of the CrN-NOW electrode material is 0.23 nm, corresponding to the (210) crystal plane of NOW, which corroborates the previous XRD characterization results.

[0033] Figure 7 This is an energy-dispersive X-ray elemental map of the CrN-NOW electrode material synthesized in Example 3 of the present invention. As shown, Cr, Ni, N, and W are evenly dispersed throughout the CrN-NOW nanorods. Cr and N each account for 2.7% of the total mass of these four elements, further demonstrating that Cr and N are uniformly incorporated into the NOW nanorods.

[0034] Figure 8 This is the energy dispersive X-ray elemental line scan of the CrN-NOW electrode material synthesized in Example 3 of the present invention. As shown in the figure, Cr, Ni, N and W elements are almost absent outside the CrN-NOW nanorod area, while the elemental line scan of the nanorod clearly shows Cr, Ni, N and W. Figure 7 The results show that Cr and N elements are uniformly modified into the NOW material.

[0035] The present invention also uses a photoelectron spectroscopy (XPS) to characterize the element bonding and electronic structure information of the material. Figure 9 Ni 2p high-resolution energy spectra of NOW, Cr-NOW, and CrN-NOW electrode materials synthesized in Comparative Examples 1 and 2 and Example 3 of the present invention. As shown in the detailed XPS spectra of Ni 2p, the classic Ni 2p can be observed near 856.62 and 874.26 eV for NOW, Cr-NOW, and CrN-NOW. 3 / 2 peak and Ni 2p 1 / 2 Peak. It was found that after Cr modification, the Ni 2p peak of Cr-NOW shifted toward a lower valence state. Further introduction of N modification further shifted the Ni in CrN-NOW toward a higher valence state by 0.94 eV. This indicates that electrons from Cr in CrN-NOW were transferred to Ni, and then electrons from Ni were transferred to the more electronegative N atoms. This demonstrates that dual modification with the non-metallic element N and the metallic element Cr comprehensively regulates and optimizes the electronic structure of Ni in CrN-NOW.

[0036] Figure 10 W 4f high-resolution energy spectra of NOW, Cr-NOW and CrN-NOW electrode materials synthesized in Comparative Examples 1, 2 and Example 3 of the present invention. As shown in the fine XPS spectra of W 4f, NOW, Cr-NOW and CrN-NOW all have the classic W 4f 5 / 2 Peak and W4f 3 / 2 Peak. It was found that after Cr modification, the W 4f peak of Cr-NOW shifted slightly toward a lower valence state. Further introduction of N modification further shifted the W in CrN-NOW toward a higher valence state by 0.36 eV. This indicates that electrons from Cr in CrN-NOW were transferred to W, and then electrons from W were transferred to the more electronegative N atoms. This indicates that the dual modification of non-metallic N and metallic Cr comprehensively regulates and optimizes the electronic structure of W in CrN-NOW.

[0037] Figure 11 Cr 2p high-resolution energy spectra of Cr-NOW and CrN-NOW electrode materials synthesized in Comparative Example 2 and Example 3 of the present invention. As shown in the fine XPS spectra of Cr 2p, both Cr-NOW and CrN-NOW have classic Cr 2p 3 / 2 peak and Cr 2p 1 / 2 After N modification, it was found that Cr in CrN-NOW shifted to a high valence state by 0.09 eV, indicating that the electrons on Cr in CrN-NOW were transferred to N, indicating that the non-metallic element N modification also regulated and optimized the electronic structure of Cr in CrN-NOW.

[0038] Figure 12This is the high-resolution N 1s spectrum of the CrN-NOW electrode material synthesized in Example 3 of the present invention. As shown in the fine XPS spectrum of N 1s, the N in CrN-NOW has two XPS peaks, corresponding to the NO and NM chemical bonds, respectively. This indicates that after N modification into CrN-NOW, it further forms chemical bonds with the O and various metal elements therein, thereby regulating and optimizing the overall electronic structure of CrN-NOW, which is mutually confirmed by the previous XPS results. Application Examples

[0039] In order to highlight the application effect of the CrN-NOW electrode material prepared in accordance with the embodiment of the present invention, the materials synthesized in Examples 1-3 and Comparative Examples 1-2 were respectively subjected to electrolysis of seawater for hydrogen evolution performance tests. The electrochemical hydrogen evolution performance of various materials was tested in a PARSTAT MC multi-channel electrochemical workstation using a three-electrode system. In the three-electrode system, the materials synthesized in Examples 1-3 and Comparative Examples 1-2 were used as working electrodes, and graphite rods and mercury / mercuric oxide electrodes were used as counter electrodes and reference electrodes, respectively. The electrolytes used for electrolysis of water for hydrogen evolution are: an alkaline electrolyte is a 1 M KOH deionized water solution, a neutral electrolyte is a 1 M PBS deionized water solution, and an acidic electrolyte is a 0.5 M H2SO4 deionized water solution. The voltage measured by the electrochemical workstation is calculated using the following formula: E RHE = E Hg / HgO + 0.0591 × pH + 0.098 was converted to a universal reversible hydrogen electrode potential. Hydrogen evolution polarization curves were measured using linear voltammetry in the voltage range of 0.075 V to -0.625 V at a scan rate of 2 mV / s.

[0040] Figure 13 The hydrogen evolution polarization curves of CrN-NOW1, CrN-NOW2, and CrN-NOW electrode materials prepared in Examples 1-3 of the present invention in an alkaline electrolyte (1M KOH) are shown in the figure. As shown in the figure, the test results show that when the Cr content is 0.008 mol / L (M), the material in Example 3 exhibits the best electrocatalytic HER performance, with an overpotential of only 17 mV required to output 10 mA / cm 2 Therefore, the CrN-NOW of Example 3 was selected to carry out a series of tests and analyses.

[0041] Figure 14 The hydrogen evolution polarization curves of NOW, Cr-NOW, and CrN-NOW electrode materials prepared in comparative examples 1, 2, and 3 in alkaline electrolyte (1 M KOH) are shown. It can be seen that the alkaline HER performance of unmodified NOW is the worst, while the alkaline HER performance of Cr-NOW is improved, but it also requires a high overpotential of 133 mV to output 10 mA / cm 2Furthermore, CrN-NOW can output 10 mA / cm with an ultra-low overpotential of only 17 mV. 2 This indicates that after the electronic structure of CrN-NOW is fully optimized by co-modification with Cr and N, its HER activity in alkaline water electrolysis is also greatly improved.

[0042] Figure 15 Comparison of hydrogen evolution polarization curves of NOW, Cr-NOW, and CrN-NOW electrode materials prepared in comparative examples 1, 2, and 3 in an acidic electrolyte (0.5 M H2SO4). It is also found that the acidic HER performance of unmodified NOW is the worst, while that of Cr-NOW is improved. Furthermore, CrN-NOW only requires an ultra-low overpotential of 59 mV to output 10 mA / cm 2 This indicates that after the electronic structure of CrN-NOW is fully optimized by co-modification with Cr and N, its HER activity in acidic water electrolysis is also greatly improved.

[0043] Figure 16 This is a comparison of the hydrogen evolution polarization curves of the NOW, Cr-NOW, and CrN-NOW electrode materials prepared in Comparative Examples 1, 2, and Example 3 in a neutral electrolyte (1M PBS). As shown in the figure, the neutral HER performance of the unmodified NOW is poor, while the neutral HER performance of the single-modified Cr-NOW is improved. Furthermore, the CrN-NOW only requires an ultra-low overpotential of 56 mV to output 10 mA / cm 2 The hydrogen evolution current density.

[0044] In summary, after the co-modification of Cr and N to comprehensively optimize the electronic structure of CrN-NOW, its HER activity in water electrolysis at all pH values ​​was greatly enhanced, regardless of acidic, neutral, or alkaline electrolytes.

[0045] Figure 17 The CrN-NOW electrode material and other HER catalysts in Example 3 of the present invention output 10 mA / cm 2 Required overpotential comparison chart. It can be found that most studied transition metal HER materials require a high overpotential greater than 30 mV, while the CrN-NOW electrode material of the present invention only requires an ultra-low overpotential of 17 mV, and its performance even exceeds that of the precious metal platinum Pt. Therefore, the HER performance of the CrN-NOW electrode material of the present invention is very excellent.

[0046] In order to further evaluate the intrinsic HER activity of the prepared materials, the present invention calculated the double-layer capacitance (C dl), because the electrochemically active surface area (ECSA) is related to the electric double layer capacitance (C dl ), so first pass through the double layer capacitance (C dl ) to calculate the ECSA. Figure 18 As shown clearly, after co-modification with Cr and N, the double layer capacitance of the material gradually increases, and the Cdl of CrN-NOW is 10.8 mF / cm 2 , which indicates that the electrochemically active surface area of ​​the material is also improved after co-modification.

[0047] In order to study the intrinsic HER activity of the prepared materials, the present invention normalized the hydrogen evolution curve using the electrochemical active area. Figure 19 The hydrogen evolution polarization curves of NOW, Cr-NOW and CrN-NOW prepared in Comparative Example 1, Comparative Example 2 and Example 3 are shown in FIG. Figure 18 The results were normalized by electrochemical active area. As shown in the figure, the normalized HER activity of the CrN-NOW material in water electrolysis is still significantly better than that of NOW and Cr-NOW, indicating that the co-modification of Cr and N to fully optimize the electronic structure of CrN-NOW has significantly enhanced its intrinsic HER activity in water electrolysis.

[0048] Figure 20 The hydrogen evolution stability test diagram of the CrN-NOW electrode material prepared in Example 3 of the present invention in an alkaline electrolyte (constant current test 100 mA / cm 2 ). It can be seen that at 100 mA / cm 2 At a high hydrogen evolution current density, the CrN-NOW material can stably evolve hydrogen for more than 100 h in an alkaline electrolyte (continuous operation for more than 4 days), indicating that the CrN-NOW electrode material of this application has good alkaline HER stability.

[0049] Figure 21 The hydrogen evolution stability test diagram of the CrN-NOW electrode material prepared in Example 3 of the present invention in an acidic electrolyte (constant current test 100 mA / cm 2 ). It can be seen that at 100 mA / cm 2 Under high hydrogen evolution current density, the CrN-NOW material can stably evolve hydrogen for more than 100 h in acidic electrolyte (continuous operation for more than 4 days), indicating that the CrN-NOW material of this application has good acidic HER stability.

[0050] Figure 22 The long-term hydrogen evolution stability test diagram of the CrN-NOW material prepared in Example 3 of the present invention in a neutral electrolyte (constant current test 100 mA / cm 2 ). It can be seen that at 100 mA / cm2 Under high hydrogen evolution current density, the CrN-NOW material can stably evolve hydrogen for more than 100 h in a neutral electrolyte (continuous operation for more than 4 days), indicating that the CrN-NOW material of this application has good neutral HER stability.

[0051] Based on the above structural and performance characterizations, the study found that after co-modification with Cr and N, the electronic structure of CrN-NOW was comprehensively optimized, and its intrinsic HER activity was greatly improved, thus making the material have very excellent hydrogen evolution performance in full pH water electrolysis.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A chromium-nitrogen co-modified nickel tungstate full pH hydrogen evolution electrode material, characterized by: The electrode material is obtained by synthesizing nickel tungstate nanorods co-modified with chromium and nitrogen on the base material using foamed iron, foamed cobalt or foamed nickel as the base material.

2. The chromium-nitrogen co-modified nickel tungstate hydrogen evolution electrode material according to claim 1, characterized in that: The chromium-nitrogen co-modified nickel tungstate nanorods have a radius of 500-1800 nm and a length of 4-15 μm.

3. The chromium-nitrogen co-modified nickel tungstate hydrogen evolution electrode material according to claim 1 or 2, characterized in that: The Cr element in the electrode material is 0.5%-5% of the total mass of Ni, W, N, and Cr, and preferably 1.0%-3.5%.

4. The chromium-nitrogen co-modified nickel tungstate hydrogen evolution electrode material according to claim 1 or 2, characterized in that: The N element in the electrode material is 0.5%-5% of the total mass of Ni, W, N, and Cr, and preferably 1.0%-3.5%.

5. The method for preparing a chromium-nitrogen co-modified nickel tungstate hydrogen evolution electrode material according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Pretreatment: Wet the surface of the substrate with anhydrous ethanol, let it dry naturally, then soak it in a dilute hydrochloric acid solution to remove surface impurities, then wash it with water and anhydrous ethanol in sequence, and dry it naturally before use; (2) Hydrothermal reaction: nickel salt, tungstate and nitrate are dissolved in deionized water to obtain a hydrothermal reaction solution, and then the pretreated substrate material is immersed in the hydrothermal reaction solution for hydrothermal reaction. After the reaction is completed, the product is taken out, rinsed with deionized water and dried naturally to obtain nickel tungstate hydrate; (3) Chromium modification: A certain concentration of chromium salt solution is used as the hydrothermal reaction solution, and the obtained nickel tungstate hydrate is immersed in the hydrothermal reaction solution for hydrothermal reaction. After the reaction is completed, the product is taken out, rinsed with deionized water, and then naturally dried to obtain Cr-modified nickel tungstate hydrate; (4) Nitrogen modification: In a tube furnace, urea was used as the N source, and Cr-modified nickel tungstate hydrate was used as the modified substance. The temperature was raised to 500 °C at a rate of 2 °C / min under nitrogen or Ar atmosphere and the reaction was kept at this temperature for 2 h. The nitrogen source was provided by the decomposition of urea, and then nitrogen modification was carried out on Cr-NOW by chemical vapor deposition to obtain chromium-nitrogen co-modified nickel tungstate full pH hydrogen evolution electrode material.

6. The method for preparing a chromium-nitrogen co-modified nickel tungstate hydrogen evolution electrode material according to claim 5, characterized in that: The nickel salt in step (2) is nickel chloride with a concentration of 0.01-0.09 mol / L; the tungstate is ammonium tungstate with a concentration of 0.001-0.009 mol / L; the nitrate is sodium nitrate with a concentration of 0.01-0.1 mol / L; the temperature of the hydrothermal reaction is 120-180°C, and the time is 1-15 h.

7. The method for preparing a chromium-nitrogen co-modified nickel tungstate hydrogen evolution electrode material according to claim 5, characterized in that: The chromium salt solution in step (3) is 0.001-0.015 mol / L.

8. The method for preparing a chromium-nitrogen co-modified nickel tungstate hydrogen evolution electrode material according to claim 5, characterized in that: The hydrothermal reaction temperature in step (3) is 90-180°C, and the reaction time is 1-9 h.

9. The method for preparing a chromium-nitrogen co-modified nickel tungstate hydrogen evolution electrode material according to claim 5, characterized in that: The amount of urea used in step (4) is 0.1-1.9 g.

10. Use of a chromium-nitrogen co-modified nickel tungstate full pH hydrogen evolution electrode material according to any one of claims 1 to 4 in hydrogen production by electrolysis of seawater.

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