Preparation method of Ni2P / MoOx / Fe2P nanorod electrocatalyst

Abstract

The invention belongs to the field of nano material preparation, and discloses a nickel-molybdenum-iron compound growing on foamed nickel and a preparation method and application of an anion exchange membrane. The difunctional electrocatalyst Ni2P / MoOx / Fe2P with an amorphous MoOx and crystal Ni2P / Fe2P heterogeneous structure is prepared through a hydrothermal-etching-phosphating method. Ni2P / MoOx / Fe2P is used as a cathode and an anode, an overall water decomposition (OWS) performance test is carried out in an electrolyte containing 1M of KOH, and the required voltage is only 1.815 V when the current density reaches the large current density of 250mA cm < 2 >. This is attributed to sufficient active sites, abundant phase interfaces and a unique nanorod array structure in the nickel-molybdenum-iron compound. The material still has excellent stability under the ultrahigh constant current density of 500 mA cm < 2 >. The PVA / PDDA-OH <-> membrane with anion selectivity is prepared through physical crosslinking of PVA and PDDA, and the PVA / PDDA-OH <-> membrane has good OH <-> conductivity. The anion exchange membrane water electrolyzer assembled by using the Ni2P / MoOx / Fe2P catalyst and PVA / PDDA-OH <-> stably operates for 250 hours under the current density of 1 A cm <-2 >, the hydrogen production Faraday efficiency is about 94.8% through calculation, and the potential of the anion exchange membrane water electrolyzer in the actual application of large-current hydrogen production is highlighted.

Description

Technical Field

[0001] The present invention belongs to the field of nanomaterial preparation, and particularly relates to a preparation method of a nickel-molybdenum-iron complex grown on nickel foam as a bifunctional catalyst and an anion exchange membrane, and the application of the composite to an anion exchange membrane water electrolyzer. Background Art

[0002] The technology of hydrogen production by water electrolysis has become a research focus in the field of renewable energy conversion due to its environmental friendliness. In industrial applications, the electrolysis of water under high current conditions places higher requirements on the catalyst system - it is necessary to reduce the overpotential to improve energy efficiency, and to ensure long-term stability under high current density. At present, platinum-carbon composite catalysts (Pt / C) are commonly used as catalytic materials for the hydrogen evolution reaction (HER), while the catalytic oxygen evolution reaction (OER) process relies on iridium oxide (IrO2) catalysts. However, precious metal-based catalysts have the problems of low content and high price, which has prompted researchers to develop new non-precious metal-based electrocatalysts to reduce the cost of hydrogen production and significantly improve the material's performance at high current density (>500 mA cm) while maintaining high catalytic activity. -2 ) under durability.

[0003] The uniquely strong electronegativity of phosphorus in transition metal phosphides (TMPs) optimizes the adsorption energy of hydrogen intermediates, enabling them to exhibit exceptional HER performance, making it a research focus in this field. Atomic-scale analysis reveals that the ordered integration of phosphorus into the transition metal lattice produces multiple synergistic effects. First, the spatial occupancy of phosphorus atoms increases the interatomic distances between metal atoms, weakening intermetallic interactions, inducing a d-band contraction and increasing the density of states near the Fermi level, while also endowing the material with excellent electron transport properties. At the thermodynamic level, phosphorus alloying strategies can significantly reduce the dissolution of metal components, thereby simultaneously improving the catalyst's structural stability and corrosion resistance. More importantly, under anodic potential, phosphorus species undergo controlled oxidation to form phosphates, a process that induces controlled lattice distortion on the catalyst surface. This structural reconstruction not only promotes wetting at the electrode / electrolyte interface but also significantly enhances the adsorption and activation of water molecules by creating hydrophilic active sites, ultimately leading to a substantial improvement in the OER reaction kinetics. Therefore, the development of more efficient TMPs catalysts is crucial for high-current hydrogen production. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a method for preparing a nickel-molybdenum-iron composite grown on nickel foam as a bifunctional catalyst.

[0005] Another object of the present invention is to provide a nickel-molybdenum-iron composite prepared by the above method.

[0006] Another object of the present invention is to provide the use of the nickel-molybdenum-iron composite prepared by the above method in an anion exchange membrane water electrolyzer.

[0007] The purpose of the present invention is achieved through the following solutions: (1) The nickel foam was placed in hydrochloric acid and ethanol solutions in sequence for ultrasonic treatment, and then dried to obtain product 1; (2) dissolving the nickel source and the molybdenum source in deionized water to obtain solution 1, transferring solution 1 to a reactor, and performing a hydrothermal reaction to obtain product 2; (3) Transferring product 2 to a solution containing an iron source for etching to obtain product 3; (4) The product 3 and the phosphorus source are placed in a tube furnace for low-temperature phosphating treatment, and finally a nickel-molybdenum-iron composite grown on nickel foam is obtained, which is recorded as Ni2P / MoO x / Fe2P.

[0008] In step (1), the ethanol solution is analytical grade and the treatment time is 10-15 minutes. The hydrochloric acid solution is 3-5 mol / L and the treatment time is 10-15 minutes. The drying temperature is 60-80 °C and the drying time is 1-6 hours. In step (2), the nickel source can be selected from at least one of nickel acetate, nickel nitrate and nickel chloride, and the amount added to the aqueous solution is 7.9-9.76 g / L; the molybdenum source can be selected from at least one of sodium molybdate, potassium molybdate and ammonium molybdate, and the amount added to the aqueous solution is 7.93-8.03 g / L, the hydrothermal reaction temperature is 140-160°C, the drying temperature is 60-80°C, and the drying time is 1-6 hours; In step (3), the iron source can be selected from K3[Fe(CN)6], etc. The amount of the iron source added in the aqueous solution is 6~10 g / L, the etching temperature is 85~90 ℃, and the etching time is 1~2 h; In step (4), the amount of phosphorus source added is 1-1.5 g, and the product 3 and the phosphorus source are placed in the downstream and upstream areas of the tube furnace, respectively, at a reaction temperature of 350-400 °C.

[0009] A nickel-molybdenum-iron composite grown on nickel foam is prepared by the above method.

[0010] The nickel-molybdenum-iron composite grown on nickel foam prepared by the above method is used as a bifunctional catalyst (i.e., catalytic hydrogen evolution at the cathode and catalytic oxygen evolution at the anode) in an anion exchange membrane water electrolyzer.

[0011] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The raw materials of the present invention are abundant in source and low in cost. It can be prepared at 140°C to 160°C. The preparation process is simple, the experimental cycle is short, and the repeatability is high.

[0012] 2. Ni2P / MoO prepared by the present invention x / Fe2P has excellent bifunctional catalytic performance. In 1 M KOH alkaline electrolysis cell, Ni2P / MoO x / Fe2P catalyst for hydrogen evolution at 10 mA cm -2 The overpotential at a current density of 53 mV was 53 mV. In addition, the overpotential at 250 mA cm -2 After 24 h of continuous electrolysis at high current density, Ni2P / MoO x / Fe2P has no obvious attenuation of potential, while Ni2P / MoO x The catalytic oxygen evolution of the Fe2P catalyst only requires an applied potential of 1.473 V to reach 10 mA cm -2 The current density was 250 mA cm -2 After stable operation at 1.600 V (vs. RHE) for 24 hours at a current density of 1.600 V (vs. RHE), Ni2P / MoO x / Fe2P potential still has no obvious attenuation; in the overall water splitting (OWS) performance test with 1 M KOH as the electrolyte, at 10 mA cm -2 The cell voltage at the current density was 1.431 V, while the −2 The voltage required at high current density is only 1.815 V. x The Fe2P electrode was applied to an anion exchange membrane water electrolyzer system on a large scale. In a 250-hour constant current stability test, the voltage-time curve showed no step decay, and the decay rate was only 160 μV h -1 ; Through research, it was found that the Faraday efficiency of hydrogen production is about 94.8%.

[0013] 3. Ni2P / MoO prepared by the present invention x / Fe2P catalyst is composed of crystalline Ni2P / Fe2P and amorphous MoO x This unique structural configuration exhibits a significant synergistic enhancement effect: amorphous MoO x Through its dynamic surface reconstruction ability, it can continuously expose fresh active sites during the electrocatalytic process; and the highly crystalline Ni2P / Fe2P bimetallic phosphide promotes rapid charge transfer through a compact lattice. The heterogeneous structure catalyst prepared by this method maintains a nanorod array structure with a nanorod diameter of approximately 350 nm. In-depth analysis shows that Ni2P / MoO xThe excellent OER stability of / Fe2P is attributed to the following synergistic effects: the in situ generated amorphous NiFeOOH, acting as the true active phase, boasts a rich hydroxylated surface and defective structure, significantly enhancing the adsorption / desorption efficiency of intermediates. Simultaneously, the progressive leaching of Mo and P not only does not destroy active sites but, through surface roughening, exposes more active surface area, optimizing mass transfer between the electrolyte and the catalytic interface. This "self-optimizing" electrochemical reconstruction mechanism enables the material to achieve both high activity and long life at industrial-grade current densities.

[0014] 4. The present invention also discloses the use of the nickel-molybdenum-iron composite grown on nickel foam as a bifunctional catalyst in an anion exchange membrane water electrolyzer.

[0015] The present invention also provides a method for preparing the anion exchange membrane.

[0016] Another object of the present invention is to provide an anion exchange membrane prepared by the above method.

[0017] Another object of the present invention is to provide an application of the anion exchange membrane prepared by the above method in an anion exchange membrane water electrolyzer.

[0018] The purpose of the present invention is achieved through the following solutions: (1) Dissolve polyvinyl alcohol (PVA) in deionized water and place in a constant temperature water bath to obtain product 1; (2) Product 1 is mixed with a polydimethylammonium chloride (PDDA) aqueous solution in proportion and stirred to obtain product 2; (3) Product 2 is evenly coated on the surface of the substrate and placed in a vacuum drying oven for curing to obtain product 3; (4) Product 3 is immersed in a specific solution for ion exchange to obtain product 4, which is recorded as PVA / PDDA-OH - membrane.

[0019] In step (1), the degree of alcoholysis of polyvinyl alcohol is 95-99%, the amount added to the aqueous solution is 103.4-120 g / L, and the water bath temperature is 80-90 °C.

[0020] In step (2), the mass fraction of PDDA is 15-20 wt%, the molecular weight is 400,000-500,000, the mixing ratio of PVA to PDDA is 2:1, and the stirring time is 2-2.5 h; In step (3), the substrate is a polytetrafluoroethylene (PTFE) substrate, the drying temperature is 50-60 °C, and the curing time is 24-30 h; In step (4), the soaking solution is a 54.5-57 g / L potassium hydroxide solution, and the soaking time is 21-24 h.

[0021] An anion exchange membrane prepared by the above method.

[0022] The anion exchange membrane prepared by the above method is used in an anion exchange membrane water electrolyzer.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The raw materials of the present invention are abundant in source, pollution-free and highly reproducible.

[0024] 2. The present invention produces PVA / PDDA-OH with anion selectivity - Membrane, thickness 400 μm, membrane OH - The conductivity reached 55.5 mS cm -1 In addition, during the preparation process, the PVA molecular chains form a physical cross-linking network with PDDA through crystallization, forming a PVA / PDDA primary film with uniform thickness.

[0025] 4. The present invention also discloses the application of the above anion exchange membrane in an anion exchange membrane water electrolyzer. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Ni2P / MoO prepared in Example 1 x / Fe2P catalyst synthesis flow chart.

[0027] Figure 2 Ni2P / MoO prepared in Example 1 x / Fe2P and NiMoO4 and NiMoO4@PBA prepared in Comparative Examples 1 and 2, where (a) is Ni2P / MoO x / Fe2P, NiMoO4 and NiMoO4@PBA; (b) XRD patterns of Ni2P / MoO x Raman pattern of / Fe2P.

[0028] Figure 3 These are scanning electron microscope (SEM) images of NiMoO4 and NiMoO4@PBA prepared in Comparative Examples 1 and 2, where (a) is the SEM image of the NiMoO4 precursor, and (b) is the SEM image of the NiMoO4@PBA precursor.

[0029] Figure 4 Ni2P / MoO prepared in Example 1 x Scanning electron microscopy (SEM), transmission electron microscopy (HRTEM) and high-resolution transmission electron microscopy (HRTEM) images of / Fe2P, where (a) is the SEM image, (b) is the TEM image, (c) (d) are HRTEM images, and (e) is the EDS image.

[0030] Figure 5 Ni2P / MoO prepared in Example 1 x / Fe2P and Comparative Examples 1 and 2 prepared NiMoO4 and NiMoO4@PBA XPS full spectrum and high resolution XPS spectrum, where (a) is Ni2P / MoO x / Fe2P, NiMoO4@PBA and NiMoO4 XPS full spectra; (b) Mo 3d High-resolution XPS spectrum; (c) Ni 2p High-resolution XPS spectrum; (d) Fe 2p High-resolution XPS spectrum; (e) is P 2p High-resolution XPS spectrum.

[0031] Figure 6 Ni2P / MoO prepared in Example 1 x / Fe2P and NiMoO4, NiMoO4@PBA, Ni2P / MoO4 prepared in Comparative Examples 1, 2, 3 and 4 x Electrochemical performance characterization of the cathode catalytic hydrogen evolution reaction of Ni2P / MoO and Pt / C, where (a) is Ni2P / MoO x / Fe2P,Ni2P / MoO x , NiMoO4@PBA, NiMoO4 and Pt / C at 1.0 M Linear sweep cyclic voltammetry (LSV) curve under KOH electrolyte; (b) η 250 Histogram; (c) Tafel Slope; (d) is the Nyquist impedance spectrum; (e) is the capacitance diagram; (f) is the CP curve.

[0032] Figure 7 Ni2P / MoO prepared in Example 1 x / Fe2P and NiMoO4, NiMoO4@PBA, Ni2P / MoO4 prepared in Comparative Examples 1, 2 and 3 x Cyclic voltammetry (CV) curves in hydrogen evolution reaction, where (a) is Ni2P / MoO x / Fe2P; (b) CV curve of Ni2P / MoO x CV curve of (c) NiMoO4@PBA; (d) NiMoO4.

[0033] Figure 8 Ni2P / MoO prepared in Example 1 x / Fe2P and NiMoO4, NiMoO4@PBA, Ni2P / MoO4 prepared in Comparative Examples 1, 2, 3 and 4 x Electrochemical performance characterization of the cathode catalytic oxygen evolution reaction of Ni2P / MoO and Pt / C, where (a) is Ni2P / MoO x / Fe2P, NiMoO4, NiMoO4@PBA, Ni2P / MoO x and RuO2 at 1.0 M Linear sweep cyclic voltammetry (LSV) curve under KOH electrolyte; (b) η 250 Histogram; (c) Tafel Slope; (d) is the Nyquist impedance spectrum; (e) is the capacitance diagram; (f) is the CP curve.

[0034] Figure 9 Ni2P / MoO prepared in Example 1 x / Fe2P and NiMoO4, NiMoO4@PBA, Ni2P / MoO4 prepared in Comparative Examples 1, 2 and 3 x Cyclic voltammetry (CV) curves in the oxygen evolution reaction, where (a) is Ni2P / MoO x / Fe2P; (b) CV curve of Ni2P / MoO x CV curve of (c) NiMoO4@PBA; (d) NiMoO4.

[0035] Figure 10 Ni2P / MoO prepared in Example 1 x LSV curve and Nyquist impedance spectrum of / Fe2P before and after HER test, where (a) is LSV curve; (b) is Nyquist impedance spectrum.

[0036] Figure 11 Ni2P / MoO prepared in Example 1 x Phase characterization of / Fe2P before and after HER test, where (a) is XRD pattern; (b) is XPS full spectrum; (c) is SEM image before test; (d) is SEM image after test; (e) is Ni 2p High-resolution XPS spectrum (f) is Fe 2p High-resolution XPS spectrum (g) for Mo 3d High-resolution XPS spectrum (h) is P 2p High-resolution XPS spectrum.

[0037] Figure 12 Ni2P / MoO prepared in Example 1 xLSV curves and Nyquist impedance spectra of / Fe2P before and after OER test, where (a) is the LSV curve, (b) is the Nyquist impedance spectrum, and (c) is the Fresh LSV curve.

[0038] Figure 13 Ni2P / MoO prepared in Example 1 x Phase characterization of / Fe2P before and after OER test, where (a) is XRD pattern; (b) is XPS full spectrum; (c) is SEM image before stability test; (d) is SEM image after stability test; (e) is Ni 2p High-resolution XPS spectrum of Fe 2p High-resolution XPS spectrum of Mo 3d High-resolution XPS spectrum of P 2p High-resolution XPS spectrum.

[0039] Figure 14 PVA / PDDA-OH prepared in Example 2 - Synthesis routes of anion exchange membranes.

[0040] Figure 15 PVA / PDDA-OH prepared in Example 2 - Characterization of anion exchange membrane, where (a) is the infrared spectrum (FTIR spectrum); (b) is the Nyquist impedance spectrum.

[0041] Figure 16 Schematic diagram of the reaction and internal structure of the anion exchange membrane water electrolyzer (AEMWE).

[0042] Figure 17 Anion exchange membrane water electrolyzer (AEMWE) and its electrochemical characterization, where (a) is AEMWE; (b) is LSV curve; (c) is CP curve.

[0043] Figure 18 Schematic diagram of hydrogen production at AEMWE, where (a) is the hydrogen production device; (b) is the gas flow diagram; and (c) is the Faraday efficiency of hydrogen production. DETAILED DESCRIPTION

[0044] The present invention will be described in further detail below with reference to the Examples and accompanying drawings, but the embodiments of the present invention are not limited thereto. Where specific conditions are not specified in the Examples, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used, where the manufacturer is not specified, are commercially available conventional products.

[0045] 1. Example 1 A method for preparing a nickel-molybdenum-iron composite grown on nickel foam as a bifunctional catalyst is provided. The method comprises the following steps: (1) Place 3 cm × 3 cm nickel foam in 3 M hydrochloric acid for 15 minutes to remove the surface nickel oxide layer. Then place the nickel foam in anhydrous ethanol for 15 minutes to completely remove the organic residue and dry it in vacuum at 60 °C. (2) Dissolve 1 mmol nickel nitrate and 1 mmol sodium molybdate in 30 mL aqueous solution, stir to form a homogeneous solution, and place it together with the dried nickel foam in step (1) in a 50 mL polytetrafluoroethylene-lined autoclave. Hydrothermal reaction is carried out at 150°C for 6 h, and then washed and dried to obtain product 2: (3) Product 2 was transferred to a reaction system containing 30 mL of K3[Fe(CN)6] etching solution (8 mg / mL) and surface etching was performed at 90 °C for 1 h to obtain product 3; (4) The product 3 and the phosphorus source NaH2PO2 were placed in the downstream and upstream areas of the tube furnace respectively. Under the protection of Ar atmosphere, the temperature was raised to 350 °C at 2.5 °C / min and kept constant for 2 h. Finally, the nickel-molybdenum-iron composite was loaded on the nickel foam and was recorded as Ni2P / MoO x / Fe2P: Example

[0046] A method for preparing an anion exchange membrane (AEM) with high ionic conductivity comprises the following steps: (1) Accurately weigh 6 g of polyvinyl alcohol (PVA) powder (alcoholysis degree: 98-99 mol%), dissolve it in 54 mL of deionized water, and continue stirring in a constant temperature water bath at 90°C until the solution becomes transparent and uniform to obtain product 1; (2) Product 1 was precisely mixed with a polydimethylammonium chloride (PDDA) aqueous solution (20 wt%, molecular weight 400,000-500,000) in a mass ratio of 2:1, and magnetically stirred for 2 h to form a homogeneous transparent composite sol to obtain product 2; (3) Product 2 was evenly coated on the surface of a polytetrafluoroethylene (PTFE) substrate and placed in a vacuum drying oven at 60°C for curing for 24 h to obtain product 3; (4) Product 3 was immersed in 1 M KOH solution for ion exchange for 24 h to obtain product 4, which was recorded as PVA / PDDA-OH - membrane.

[0047] Comparative Example 1 The preparation of NiMoO4 refers to the preparation method of Example 1, and no iron source and phosphorus source need to be added during the synthesis process.

[0048] Comparative Example 2 The preparation of NiMoO4@PBA refers to the preparation method of Example 1, and no phosphorus source needs to be added during the synthesis process.

[0049] Comparative Example 3 Ni2P / MoO x The preparation method of Example 1 is referred to, and ion exchange etching is not required during the synthesis process.

[0050] Comparative Example 4 Preparation of Pt / C / NF and RuO2 / NF: First, 8 mg of RuO2 and 20% Pt / C were added to a mixed solution of 160 μL of water, 420 μL of anhydrous ethanol and 20 μL of Nafion, respectively. The mixture was ultrasonically oscillated for 40 minutes to form a uniform suspension. The suspension was then evenly dropped onto nickel foam with an area of ​​1 cm × 1 cm using a pipette and dried at 60°C to obtain RuO2 / NF and 20% Pt / C / NF.

[0051] Electrochemical testing of the catalyst's catalytic oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance was conducted using both three-electrode and two-electrode systems. The test response signals were recorded by a computer connected to an electrochemical workstation (CHI660E). In the three-electrode system, a platinum electrode holder was used as the working electrode, securing a 1cm×1cm nickel foam loaded with the catalyst. A graphite rod was used as the counter electrode, and a mercury-mercury oxide (Hg / HgO) electrode (Hg / HgO) was used as the reference electrode. The reference electrode was immersed in a 1M KOH solution before use to ensure the accuracy of the test results. In the two-electrode system used for complete water splitting performance testing, the working electrode was connected to a platinum electrode holder, while the counter and reference electrodes were connected to another identical platinum electrode holder. The data was processed after the test. The test solution was 1 M KOH, and the potential of the mercury-mercury oxide electrode (Hg / HgO) needed to be converted to the potential of the RHE reversible hydrogen electrode: E(vs. RHE) = E(vs. Hg / HgO) + 0.059×PH + 0.098 = E(vs. Hg / HgO) + 0.924.

[0052] About Example 1 and Comparative Examples 1, 2, 3, and 4 Figure 1 Ni2P / MoO prepared in Example 1 x / Fe2P synthesis flow chart.

[0053] Figure 2 Ni2P / MoO prepared in Example 1 xPhase characterization of NiMoO4 and NiMoO4@PBA prepared from the comparative examples 1 and 2. Figure (a) shows the high purity and good crystallinity of the Ni2P crystal phase and the presence of a heterogeneous structure of Ni2P-Fe2P bimetallic phosphide in the material, while no MoO was observed in the XRD pattern. x However, in Figure (b), we can see that the Raman shift is 700 cm -1 The vibration peaks appearing near the Mo-O-Mo symmetric stretching vibration mode correspond to the Mo-O-Mo symmetric stretching vibration mode. Combined with XRD characterization, it can be seen that MoO x Exists in amorphous form.

[0054] Figure 3 Scanning electron microscopy (SEM) images of NiMoO4 and NiMoO4@PBA prepared in Comparative Examples 1 and 2. Figure (a) shows that the NiMoO4 precursor exhibits a regular nanorod array structure with a diameter of approximately 200 nm and a smooth surface. Figure (b) shows that after K3[Fe(CN)6] chemical etching, the NiMoO4@PBA precursor retains its original nanorod array structure, but the nanorod diameter increases significantly, which is due to the volume expansion effect caused by the etching.

[0055] Figure 4 Ni2P / MoO prepared in Example 1 x Scanning electron microscope (SEM), transmission electron microscope (HRTEM) and high-resolution transmission electron microscope (HRTEM) images of Ni2P / MoO / Fe2P. From Figures (a to b), we can see that the Ni2P / MoO formed by the subsequent phosphating treatment x The / Fe2P heterogeneous structure still inherits the array structure of the precursor, with a diameter of about 350 nm and a significantly roughened surface. During this process, a multi-stage phase transition occurs: (1) NaH2PO2 decomposes at 300 °C to produce PH3 gas; (2) PH3 reacts chemically with metal oxides, where the NiMoO4 core is converted into Ni2P / MoO x The surface PBA layer is phosphated to form a Fe2P shell; (3) By adjusting the phosphating temperature and time, the crystalline Ni2P / Fe2P and amorphous MoO xInterface coupling. Figures (cd) show the unique amorphous-crystalline heterogeneous structure of the material. Through lattice fringe analysis, it was found that the interplanar spacing of 0.221 nm and 0.205 nm correspond to the (111) crystal plane of Ni2P and the (201) crystal plane of Fe2P, respectively, and the phase interface between the metal phosphide crystal phase and the amorphous phase was clearly observed, which is highly consistent with the XRD spectrum results. This amorphous / crystalline heterogeneous structure can improve the charge transfer efficiency by constructing a continuous ion conduction channel, while exposing a high density of unsaturated coordination active sites. In addition, Figure (e) confirmed the formation of a strong electronic coupling phase interface through element distribution analysis to promote the adsorption / desorption kinetics of reaction intermediates. Furthermore, Mo, O, Ni, Fe, and P elements are uniformly dispersed. Based on the above analysis, a nanoarray catalyst with a multi-level heterogeneous interface was successfully constructed through a multi-step preparation strategy of hydrothermal-etching modification-phosphating reconstruction.

[0056] Figure 5 Ni2P / MoO prepared in Example 1 x / Fe2P and NiMoO4 and NiMoO4@PBA prepared in comparative examples 1 and 2. Figure (a) confirms that Ni2P / MoO x / Fe2P contains five characteristic element signals: Ni, Fe, O, Mo, and P. In Figure (b), the signal at 230.6 eV ( 3d 5 / 2 ) and 233.9 eV ( 3d 3 / 2 ) corresponds to the characteristic peak of Mo 4+ species, while those at 232.6eV and 235.9eV are attributed to Mo 6+ Compared with the NiMoO4@PBA precursor, the valence of Mo is reduced after phosphating, but no Mo-P characteristic peak is detected. This is attributed to the high MoP formation temperature (>850 ℃), while the actual phosphating temperature is only 350 ℃, so Mo-P cannot be generated. Figure (c) shows the typical double spin-orbit splitting characteristics, and the peaks at 857.1 eV and 874.8 eV are attributed to Ni 2+ , while at 853.3 eV ( 2p 3 / 2 ) and 870.7 eV ( 2p 1 / 2 The characteristic peaks of ) correspond to the Ni-P bond of metal phosphide, confirming the successful formation of Ni2P. The characteristic peaks at 710.7 eV and 724.2 eV in Figure (d) correspond to the Ni-P bond of Fe 2+ The characteristic peaks at 713.4 eV and 727.2 eV correspond to Fe 3+ , while at 706.6 eV ( 2p3 / 2 ) and 719.4 eV ( 2p 1 / 2 ) appears a new Fe-P characteristic peak, confirming the successful formation of Fe2P. In Figure (e), the peak at 129.8 eV ( 2p 3 / 2 ) and 130.9 eV ( 2p 1 / 2 The characteristic peaks of ) correspond to the PM bond of metal phosphide, while the peaks at 134.2 eV and 135.3 eV are derived from the PO species formed by surface oxidation. 2p 3 / 2 and Ni 2p 3 / 2 The binding energy shifts toward the higher binding energy end by 1.4 eV and 0.9 eV compared to the precursor, further confirming the enrichment of high-valent metal species, which can serve as efficient OER active sites. It also indicates that the electron cloud density of the Ni / Fe center is reduced. This electron-depleted state is beneficial for optimizing the adsorption strength of the OER intermediate (HOO*). The shift in binding energy confirms the strong electronic interaction at the heterophase interface, which is conducive to water electrolysis.

[0057] Figure 6 Ni2P / MoO prepared in Example 1 x / Fe2P and NiMoO4, NiMoO4@PBA, Ni2P / MoO4 prepared in Comparative Examples 1, 2, 3 and 4 x Electrochemical performance characterization of the cathode catalytic hydrogen evolution reaction of Ni2P / MoO and Pt / C. As shown in Figures (a-b), the LSV curve test shows that Ni2P / MoO x The / Fe2P catalyst exhibited excellent HER catalytic activity at a current density of 10 mA cm -2 The overpotential when η 10 ) is only 53 mV. When the current density is increased to 250 mA cm -2 When the overpotential ( η 250 ) is 214 mV; this performance is significantly better than the comparative material Ni2P / MoO x ( η 10 = 78 mV, η 250 = 359 mV)、NiMoO4@PBA( η 10 = 223 mV, η 250 = 530 mV) and NiMoO4 ( η 10= 187 mV, η 250 = 517 mV), even at 250 mA cm -2 The performance at high current density exceeds that of commercial Pt / C catalysts ( η 250 = 253 mV). Figure (c), Ni2P / MoO x / Fe2P Tafel The slope is 77.54mV dec -1 , close to 52.45 mV dec of Pt / C -1 , and is better than Ni2P / MoO x (111.22 mV dec -1 ), NiMoO4@PBA (201.29 mV dec -1 ) and NiMoO4 (244.30 mV dec -1 ), indicating that it has a fast Volmer-Heyrovsky reaction kinetics mechanism. Figure (d) further reveals the charge transfer resistance of the material ( R ct ) is only 1.23 Ω, which is significantly lower than that of the comparative sample (Ni2P / MoO x : 2.77 Ω; NiMoO4@PBA: 30.66 Ω; NiMoO4: 20.56 Ω), indicating that it has the best charge transport ability. As shown in Figure (e), Ni2P / MoO x / Fe2P has the largest C dl Value (87.20 mF cm -2 ), greater than Ni2P / MoO x (55.90 mF cm -2 )、NiMoO4@PBA(2.56 mF cm -2 ) and NiMoO4 (2.81 mF cm -2 ), confirming that it has the largest electrochemically active surface area (ECSA). The larger electrochemically active area in the catalyst helps the bubbles formed on the electrode surface to escape in time, reducing the impact of bubbles on the electrode structure, alleviating the influence of stress generated during the electrochemical reaction on the structure, and improving the stability and service life of the heterostructure. In addition, by constant current method, at 250 mA cm -2 Evaluation of Ni2P / MoO at high current density x / Fe2P, as shown in Figure (f), after 24 h of continuous electrolysis, Ni2P / MoO x / Fe2P potential has no obvious decay, indicating that the material has excellent catalytic stability.

[0058] Figure 7 Ni2P / MoO prepared in Example 1 x / Fe2P and NiMoO4, NiMoO4@PBA, Ni2P / MoO4 prepared in Comparative Examples 1, 2 and 3 x Cyclic voltammetry (CV) curves in the hydrogen evolution reaction.

[0059] Figure 8 Ni2P / MoO prepared in Example 1 x / Fe2P and NiMoO4, NiMoO4@PBA, Ni2P / MoO4 prepared in Comparative Examples 1, 2, 3 and 4 x Electrochemical performance characterization of the cathode catalytic oxygen evolution reaction of Ni2P / MoO2 and RuO2. As shown in Figures (ab), Ni2P / MoO x / Fe2P at 10 mA cm -2 and 250 mA cm -2 The current density required is only 1.473 V and 1.594 V respectively, which are significantly better than Ni2P / MoO x ( E 10 = 1.516 V, E 250 = 1.721 V)、NiMoO4@PBA( E 10 =1.546 V, E 250 =1.788 V) and NiMoO4 ( E 10 =1.534 V, E 250 =1.841 V) for the comparative sample. It is noteworthy that at 250 mA cm -2 At the same current density, its potential (1.594 V) is even lower than that of commercial RuO2 catalyst (1.631 V). Figure (c) shows the catalyst Tafel Slope curve, Ni2P / MoO x / Fe2P has a smaller Tafel The slope is 58.51 mV dec -1 , compared with RuO2 (44.07 mV dec -1 ) is close, which is much lower than Ni2P / MoO x (82.46 mV dec -1 ), NiMoO4@PBA (92.62 mV dec -1 ) and NiMoO4 (108.59 mVdec -1), confirming its fast reaction kinetics. Figure (d) shows that the catalyst has the smallest R ct value (0.71 Ω), which is significantly lower than that of other samples (Ni2P / MoO x : 2.42 Ω; NiMoO4@PBA: 5.38 Ω; NiMoO4: 6.92 Ω), with the smallest charge transfer resistance, proving that the target catalyst also exhibits the fastest reaction kinetics in OER. At the same time, Figure (e) shows that Ni2P / MoO x / Fe2P C dl Value (1.31 mF cm -2 ) is also greater than Ni2P / MoO x (1.21 mF cm -2 )、NiMoO4@PBA(1.14 mF cm -2 ) and NiMoO4 (0.89 mF cm -2 ), indicating that it has the largest electrochemically active specific surface area, which provides favorable conditions for continuous catalytic reaction at high current density. The above OER performance is Ni2P / MoO x / Fe2P becomes a prerequisite for high current density oxygen evolution catalyst, but how to maintain its own structural stability in the high potential oxidation state is a key issue. Ni2P / MoO x / Fe2P can promote the formation of real active material oxyhydroxide through electrochemical reconstruction during the OER process, thereby showing excellent OER activity. As shown in Figure (f), Ni2P / MoO x / Fe2P at 250 mAcm -2 After stable operation at 1.600 V (vs. RHE) for 24 hours, there was no obvious attenuation, showing excellent durability. x / Fe2P exhibits excellent high-current OER catalytic performance.

[0060] Figure 9 Ni2P / MoO prepared in Example 1 x / Fe2P and NiMoO4, NiMoO4@PBA, Ni2P / MoO4 prepared in Comparative Examples 1, 2 and 3 x Cyclic voltammetry (CV) curves of the oxygen evolution reaction.

[0061] Figure 10The LSV curves and Nyquist impedance spectra of Ni2P / MoOx / Fe2P prepared in Example 1 before and after HER test. After the stability test, Figure (a) shows that the HER catalytic activity does not show a significant attenuation trend, while Figure (b) shows that after high current density cycling, the HER catalytic activity has not declined significantly. R ct The increase is only 0.11 Ω, which strongly confirms that Ni2P / MoO x The / Fe2P phosphide heterogeneous structure catalyst has excellent HER stability at high current density.

[0062] Figure 11 The phase characterization of Ni2P / MoOx / Fe2P prepared in Example 1 before and after HER testing. Figure (a) shows that the crystal structure of the material remains highly stable, with no phase transition or lattice distortion; Figures (cd) show that after the HER stability test, it still maintains the nanorod array structure, with no obvious corrosion or structural collapse; Figures (eh) reveal that the metal elements (Ni 2p 、Mo 3d 、Fe 2p ) remained basically unchanged before and after the test. It is worth noting that the chemical valence of phosphorus 2p The orbital binding energy shifts by 0.3 eV toward lower energies because P, acting as an active site for H2O dissociation and H* adsorption, accepts electrons for reduction, resulting in enhanced electronegativity at the phosphorus site. This facilitates optimization of the adsorption / desorption energy barrier of the hydrogen intermediate (H*) through electron adsorption, significantly improving the HER reaction kinetics. These results demonstrate that the material's phase structure, morphology, and elemental valence state exhibit excellent stability during HER catalysis, contributing to its durability in practical applications.

[0063] Figure 12 The LSV curve and Nyquist impedance spectrum of Ni2P / MoOx / Fe2P prepared in Example 1 before and after the OER test. Figure (a) shows that the LSV curve does not shift significantly after the OER stability test, and from Figure (b) we can see that the charge transfer resistance ( R ct ) increased by only 0.13 Ω, fully demonstrating its excellent stability at high current densities. Figure (c) shows that the OER activity of the reconstituted catalyst tested in fresh 1 M KOH remained highly consistent with that of the initial state, indicating that the leaching of molybdate and phosphate into the solution after reconstitution did not affect the catalytic performance.

[0064] Figure 13 The phase characterization of Ni2P / MoOx / Fe2P prepared in Example 1 before and after OER test. Figure (a) confirms that Ni2P / MoOx / Fe2P xThe / Fe2P phase gradually transforms into an amorphous NiFeOOH active phase. Figure (b) shows that the characteristic peaks of Mo and P elements disappear. Figures (cd) show that the initial regular nanoarray structure of the catalyst collapses and transforms into disordered needle-like aggregates. This crystal phase structure and morphology evolution is due to the dynamic electrochemical reconstruction behavior during the OER process. Figures (ef) further reveal the reconstruction mechanism: Ni 2p At 857.8 eV ( 2p 3 / 2 ) and 875.7 eV ( 2p 1 / 2 ) shows typical Ni 3+ characteristic peaks, and Fe 2p At 713.0 eV ( 2p 3 / 2 ) and 725.8 eV ( 2p 1 / 2 ) shows the characteristic peak of FeOOH, which together proves the formation of NiFeOOH active layer. It is worth noting that Figure (gh) shows that the surface Mo 3d and P 2p The signal completely disappeared, indicating that Mo and P were oxidized and dissolved during the OER process, and the amorphous NiFeOOH active layer obtained after reconstruction effectively improved the OER performance.

[0065] About Example 2 Figure 14 This is the synthesis route of the PVA / PDDA-OH-anion exchange membrane prepared in Example 2.

[0066] Figure 15 This is the characterization of the PVA / PDDA-OH-anion exchange membrane prepared in Example 2. As shown in Figure (a), the membrane has a -1 The broad band at 2940 cm is the OH stretching vibration absorption peak, which mainly comes from the hydroxyl groups in PVA and the water absorbed by the membrane. -1 The stretching vibration absorption peaks of CH, 1650 and 1440 cm -1 They correspond to the quaternary ammonium group and the ring carbon skeleton of PDDA, 1090 cm -1 The corresponding peak is the stretching vibration absorption peak of CO of PVA, and finally a PVA / PDDA primary film with uniform thickness is obtained. The primary film is cut into 4 cm × 4 cm specifications and pretreated in 1 M KOH solution for 24 hours to promote the Cl - With OH in the electrolyte - Ion exchange reaction occurs to produce PVA / PDDA-OH with anion selectivity -Film (thickness: 400 μm), as can be seen from Figure (b), it significantly improves the OH content of the film. - Conductivity (55.5 mS cm -1 ).

[0067] Figure 16 Schematic diagram of the reaction and internal structure of the anion exchange membrane water electrolyzer (AEMWE).

[0068] Figure 17 The anion exchange membrane water electrolyzer (AEMWE) and its electrochemical characterization are shown in Figure (a). As shown in Figure (a), a Ni2P / MoO2 membrane with a size of 2 cm × 2 cm is used. x AEMWE electrolyzer was constructed with a / Fe2P electrode and a peristaltic pump at 50 mL min -1 The electrolyte was fed into the electrolysis chamber under the drive of the IVIUM workstation for high current stability testing. As can be seen from Figure (b), in the room temperature 1 MKOH electrolyte system, the AEMWE system exhibited significant industrial-grade performance: only 2.23 V tank voltage was required to drive 1 Acm -2 Figure (c) shows that after a 250-hour constant current stability test, the voltage-time curve showed no step decay, and the decay rate was 160 μV h -1 , indicating the excellent interfacial stability between the catalyst and the membrane electrode assembly (MEA) and the high current hydrogen production potential of AEMWE.

[0069] Figure 18 Schematic diagram of hydrogen production in AEMWE. To further quantify the hydrogen production efficiency, as shown in Figure (b), a gas flow meter was used to monitor the cathode hydrogen production in real time, and the measured hydrogen production rate was 26.4 mL min -1 The hydrogen production efficiency was calculated based on Faraday's law (FE = ZnF / It), where Z is the number of electron transfers for hydrogen generation (Z = 2) and F = 96485 C·mol -1 is the Faraday constant, I = 4 A is the constant current, t is the reaction time (s), n = V / Vm is the amount of hydrogen substance, V is the experimentally measured gas volume, V m = 22.4 L·mol -1 is the standard gas molar volume. Figure (c) shows a hydrogen production Faradaic efficiency of approximately 94.8%, confirming the system's efficient electron-hydroxyl conduction and low side reaction characteristics at high current densities.

Claims

1. A method for preparing a nickel-molybdenum-iron composite grown on nickel foam, characterized in that The following steps are involved: (1) The nickel foam was placed in hydrochloric acid and ethanol solutions in sequence for ultrasonic treatment, and then dried to obtain product 1; (2) dissolving the nickel source and the molybdenum source in deionized water to obtain solution 1, transferring solution 1 to a reactor, and performing a hydrothermal reaction to obtain product 2; (3) Transferring product 2 to a solution containing an iron source for etching to obtain product 3; (4) The product 3 and the phosphorus source are placed in a tube furnace for low-temperature phosphating treatment, and finally a nickel-molybdenum-iron composite grown on nickel foam is obtained, which is recorded as Ni2P / MoO x / Fe2P.

2. The method for preparing the nickel-molybdenum-iron composite grown on nickel foam according to claim 1, wherein: In step (1), the ethanol solution is analytical grade and the treatment time is 10-15 minutes. The hydrochloric acid solution is 3-5 mol / L and the treatment time is 10-15 minutes. The drying temperature is 60-80 °C and the drying time is 1-6 hours.

3. The method for preparing the nickel-molybdenum-iron composite grown on nickel foam according to claim 1, wherein: In step (2), the nickel source can be selected from at least one of nickel acetate, nickel nitrate and nickel chloride, and the amount added to the aqueous solution is 7.9~9.76 g / L; the molybdenum source can be selected from at least one of sodium molybdate, potassium molybdate and ammonium molybdate, and the amount added to the aqueous solution is 7.93~8.03 g / L, the hydrothermal reaction temperature is 140~160℃, the drying temperature is 60~80℃, and the drying time is 1~6 h.

4. The method for preparing the nickel-molybdenum-iron composite grown on nickel foam according to claim 1, wherein: In step (3), the iron source can be selected from K3[Fe(CN)6], etc. The amount of the iron source added in the aqueous solution is 6~10 g / L, the etching temperature is 85~90 ℃, and the etching time is 1~2 h.

5. The method for preparing the nickel-molybdenum-iron composite grown on nickel foam according to claim 1, wherein: In step (4), the amount of phosphorus source added is 1-1.5 g, and the product 3 and the phosphorus source are placed in the downstream and upstream areas of the tube furnace, respectively, at a reaction temperature of 350-400 °C.

6. The nickel-molybdenum-iron composite grown on nickel foam according to any one of claims 1 to 5.

7. Use of the nickel-molybdenum-iron composite grown on nickel foam as claimed in claim 6 as a bifunctional catalyst (i.e., catalytic hydrogen evolution at the cathode and catalytic oxygen evolution at the anode) in an anion exchange membrane water electrolyzer.

8. A method for preparing an anion exchange membrane, characterized in that The following steps are involved: (1) Dissolve polyvinyl alcohol (PVA) in deionized water and place in a constant temperature water bath to obtain product 1; (2) Product 1 is mixed with a polydimethylammonium chloride (PDDA) aqueous solution in proportion and stirred to obtain product 2; (3) Product 2 is evenly coated on the surface of the substrate and placed in a vacuum drying oven for curing to obtain product 3; (4) Product 3 is immersed in a specific solution for ion exchange to obtain product 4, which is recorded as PVA / PDDA-OH - membrane.

9. The method for preparing an anion exchange membrane according to claim 8, wherein: In step (1), the degree of alcoholysis of polyvinyl alcohol is 95-99%, the amount added to the aqueous solution is 103.4-120 g / L, and the water bath temperature is 80-90 °C.

10. The method for preparing an anion exchange membrane according to claim 8, wherein: In step (2), the mass fraction of PDDA is 15-20 wt%, the molecular weight is 400,000-500,000, the mixing ratio of PVA to PDDA is 2:1, and the stirring time is 2-2.5 h.

11. The method for preparing an anion exchange membrane according to claim 8, wherein: In step (3), the substrate is a polytetrafluoroethylene (PTFE) substrate, the drying temperature is 50~60℃, and the curing time is 24~30h.

12. The method for preparing an anion exchange membrane according to claim 8, wherein: In step (4), the soaking solution is a 54.5-57 g / L potassium hydroxide solution, and the soaking time is 21-24 h.

13. The anion exchange membrane according to any one of claims 8 to 12.

14. Use of the anion exchange membrane according to claim 13 in an anion exchange membrane water electrolyzer.

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