A kind of electrocatalytic material for producing hydrogen by electrolysis of water and its preparation method and application

Abstract

The present invention discloses an electrocatalytic material for hydrogen production by electrolysis of water, and its preparation method and application. The method comprises the following steps: providing a titanium substrate having a surface rich in microporous structure; preparing a molybdenum oxide precursor on the titanium substrate by a constant potential deposition method in a three-electrode system to obtain a MoO3 / Ti material; mixing (NH4)2IrCl6 powder and citric acid powder in water to obtain an Ir precursor solution; placing the MoO3 / Ti material in the Ir precursor solution, immersing it at room temperature for 20-40 minutes and then drying it, and finally heating it for pyrolysis to obtain a target product c-IrOx-MoO3 / Ti, i.e., an electrocatalytic material for hydrogen production by electrolysis of water. The present invention successfully constructs a highly dispersed nano-IrO loaded on the surface of three-dimensionally staggered MoO3 sheets on a chemically etched metal titanium substrate by a constant potential deposition combined with a citric acid-assisted immersion-pyrolysis method. x The catalyst has an extremely low Ir content and exhibits high catalytic activity and long-lasting stability in acidic water oxidation reactions.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalysts, and in particular to an anode electrocatalytic material for hydrogen production by electrolysis of water, and a preparation method and application thereof. Background Art

[0002] Due to the unprecedented energy crisis and environmental degradation caused by overexploitation of fossil fuels, the search and development of new alternative energy sources is urgent. New energy sources such as solar, wind, hydro, and biomass, with their numerous advantages of being clean, renewable, and environmentally friendly, are considered the most promising energy sources for the 21st century energy revolution. However, these energy sources suffer from non-periodic fluctuations in practical applications, often requiring the integration of energy conversion and storage devices to achieve a sustainable energy supply. Hydrogen, with its high energy density and zero carbon emissions, is an ideal energy carrier. Electricity generated by renewable energy can be converted into easily storable hydrogen through water electrolysis, which can then be conveniently converted to electricity using fuel cells as needed. However, the oxygen evolution reaction (OER) on the anode side of the water electrolysis process involves a complex four-electron transfer process, and kinetic hysteresis is a key factor affecting the overall water electrolysis process. Currently, four major water electrolysis technologies are popular: alkaline electrolysis (AE), anion exchange membrane (AEM), proton exchange membrane (PEM), and solid oxide electrolysis (SOE). Among them, PEM water electrolysis devices, when coupled with renewable energy systems, have attracted much attention due to their advantages such as high electrolysis efficiency, good proton conductivity, low gas leakage, compact structure, and fast response. To improve the OER efficiency in PEM systems, it is necessary to develop high-performance electrocatalysts, but this requires the catalysts to be able to adapt to the harsh and highly corrosive environment of the anode.

[0003] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide an anode electrocatalytic material for hydrogen production by electrolysis of water, and its preparation method and application, aiming to solve the problems of poor catalytic performance and poor adaptability to highly corrosive environments of the existing anode electrocatalytic materials for hydrogen production by electrolysis of water.

[0005] The technical solutions of the present invention are as follows:

[0006] A method for preparing an anode electrocatalytic material for hydrogen production by electrolysis of water, comprising the steps of:

[0007] Providing a titanium substrate with a surface rich in microporous structure;

[0008] In a three-electrode system, a molybdenum oxide precursor is prepared on the titanium substrate by a constant potential deposition method to prepare a MoO3 / Ti material;

[0009] Ir precursor solution was prepared by mixing (NH4)2IrCl6 powder and citric acid powder in water;

[0010] The MoO3 / Ti material is placed in the Ir precursor solution, immersed at room temperature for 20-40 minutes and then dried, and finally heated for pyrolysis to obtain the target product c-IrOx-MoO3 / Ti, that is, the anode electrocatalytic material for hydrogen production by electrolysis of water.

[0011] The method for preparing the anode electrocatalytic material for hydrogen production by electrolysis of water, wherein the preparation of the titanium substrate having a surface rich in microporous structure comprises:

[0012] Immerse the titanium mesh in oxalic acid solution and chemically etch it at 80-100°C for 40-80 minutes;

[0013] The etched titanium mesh was placed in deionized water and ultrasonically cleaned to obtain a titanium substrate with a surface rich in microporous structure.

[0014] The method for preparing the anode electrocatalytic material for hydrogen production by electrolysis of water, wherein in a three-electrode system, a molybdenum oxide precursor is prepared on the titanium substrate by constant potential deposition to prepare the MoO3 / Ti material, comprising the following steps:

[0015] The titanium substrate was used as a working electrode, Hg / Hg2SO4 was used as a reference electrode, a platinum sheet was used as a counter electrode, and a mixed solution of (NH4)2MoO4 and H2SO4 was used as an electrodeposition solution, and electrodeposition was performed at a constant potential of -0.8 V (vs. RHE);

[0016] The electrodeposited titanium substrate is placed in a muffle furnace for heat treatment to obtain a MoO3 / Ti material.

[0017] The method for preparing the anode electrocatalytic material for hydrogen production by electrolysis of water comprises the following steps: placing the electrodeposited titanium substrate in a muffle furnace for heat treatment at a temperature of 300-500°C, a time of 4-6 hours, and a heating rate of 10°C min -1 .

[0018] The method for preparing the anode electrocatalytic material for hydrogen production by electrolysis of water comprises the following steps: placing the MoO3 / Ti material in the Ir precursor solution, immersing it at room temperature for 20-40 minutes, and then drying it; and finally heating it for pyrolysis treatment. In the step, the drying temperature is 60-100°C and the time is 4-6 minutes; and the pyrolysis temperature is 350-450°C and the time is 1-3 hours.

[0019] A water electrolysis hydrogen production anode electrocatalytic material is prepared by the water electrolysis hydrogen production anode electrocatalytic material preparation method of the present invention.

[0020] An application of an anode electrocatalytic material for producing hydrogen by electrolysis of water, wherein the anode electrocatalytic material for producing hydrogen by electrolysis of water according to the present invention is used for producing hydrogen by electrolysis of water.

[0021] Beneficial effect: The present invention constructs in situ highly dispersed IrO attached to three-dimensional staggered MoO3 sheets on a Ti substrate. x Nanoparticles (c-IrO x -MoO3 / Ti), the heterogeneous electrocatalytic material has an extremely low Ir content (Ir loading is ~28.35μg Ir cm -2 , or c-IrO x -MoO3 catalytic layer with Ir content less than 6 wt.%), high acidic OER activity (10 mA cm -2 The overpotential at 200 mV) and good long-term stability (100 mA cm -2 This special three-dimensional staggered MoO3 sheet structure induced by citric acid effectively promotes the formation of IrO x The particles are highly dispersed. DFT calculations show that IrO x -The electronic regulation at the MoO3 heterointerface may be through O M -O Vacancy The electronic regulation optimizes the adsorption energy of the active Ir site of the catalyst to oxygen intermediates. x The dual role of morphology control and electronic regulation provides a good experimental basis and theoretical basis for designing self-supporting Ti electrodes with extremely low Ir content for acidic water oxidation. The self-assembled PEM single cell test further verifies the c-IrO x -MoO3 / Ti electrocatalysts have great application potential in renewable energy storage and conversion systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention provides a flow chart of a method for preparing an anode electrocatalytic material for producing hydrogen by electrolysis of water.

[0023] Figure 2 Schematic diagram of the fabrication of anode electrocatalytic materials for hydrogen production by water electrolysis.

[0024] Figure 3 a is MoO3 / Ti,c-IrO x -MoO3 / Ti-100,c-IrO x / Ti XRD patterns and standard PDF cards of Ti, MoO3, IrO2, and Ir; bc is c-IrO x -HRSEM of MoO3 / Ti; de is c-IrOx -MoO3 TEM; f is the fast Fourier transform image of the selected area; g is c-IrO x -HAADF-STEM of MoO3 and its elemental energy dispersive spectrum (EDS); h is the total elemental spectrum.

[0025] Figure 4 XRD patterns of MoO3 / Ti prepared at different electrodeposition times and its corresponding impregnation-pyrolysis products.

[0026] Figure 5 In the figure, ab are HRSEM of MoO3 / Ti; cd are TEM of MoO3; e is HAADF-STEM of MoO3 and its element energy dispersive spectrum (EDS); f is Mo elemental map, g is O elemental map, and h is the total elemental spectrum.

[0027] Figure 6 HRSEM images of MoO3 / Ti and its corresponding impregnation-pyrolysis products prepared with electrodeposition time of 100s and 300s, respectively, where a is MoO3 / Ti-100, b is MoO3 / Ti-300, and c is c-IrO x -MoO3 / Ti-100, d is c-IrO x -MoO3 / Ti-300.

[0028] Figure 7 ab in the equation is c-IrO x HRSEM of / Ti, c is c-IrO x Side view of / Ti, the thickness of the iridium oxide layer supported on the titanium substrate is about 578nm; de is c-IrO x TEM; f is c-IrO x HAADF-STEM and its elemental energy spectrum (EDS); g is Ir element, h is O element, and i is the total element spectrum.

[0029] Figure 8 c-IrO x -MoO3 / Ti,IrO x -MoO3 / Ti,c-IrO x / Ti and IrO x / Ti’s XRD pattern.

[0030] Figure 9 HRSEM of catalysts prepared by citric acid-assisted impregnation-pyrolysis method and conventional impregnation-pyrolysis method, where a is MoO3 / Ti and b is IrO x -MoO3 / Ti,c is IrO x / Ti,d is c-MoO3 / Ti,e is c-IrOx -MoO3 / Ti, f is c-IrO x / Ti.

[0031] Figure 10 a is MoO3 / Ti, c-IrO x / Ti and c-IrO x -Raman spectrum of MoO3 / Ti; b is MoO3 / Ti, c-IrO x / Ti and c-IrO x -O1s XPS spectrum of MoO3 / Ti; c is MoO3 / Ti and c-IrO x -Mo 3d XPS spectrum of MoO3 / Ti; d is c-IrO x / Ti and c-IrO x -Ir 4f XPS spectrum of MoO3 / Ti.

[0032] Figure 11 Figure 3 is the hydrogen oxidation-reduction CV curve used to calibrate the Hg / Hg2SO4 reference electrode in 0.5M H2SO4 solution.

[0033] Figure 12 OER performance of the electrocatalyst in 0.5 M H2SO4 solution: (a) linear sweep voltammetry (LSV); (b) Tafel slope; (c) double layer capacitance (C dl ); (d) Comparison of OER performance of various electrocatalysts in 0.5 M H2SO4 solution: the horizontal axis is 10 mA cm -2 (e) Electrochemical impedance spectroscopy (EIS), with the inset being an enlarged image of a local area of ​​the impedance spectrum; (f) LSV curves before and after the accelerated stability test; (g) Chronopotentiometry curve.

[0034] Figure 13 Figure 2 shows the LSV curves of each catalyst in 0.5 M H2SO4 solution obtained at different electrodeposition times.

[0035] Figure 14 is the Tafel slope of each catalyst obtained at different electrodeposition times in 0.5 M H2SO4 solution.

[0036] Figure 15 Figure 2 is the EIS spectra of each catalyst obtained at different electrodeposition times in 0.5 M H2SO4 solution.

[0037] Figure 16 is the C of each catalyst obtained at different electrodeposition times in 0.5 M H2SO4 solution dl .

[0038] Figure 17 c-IrO x -MoO3 / Ti at 50 mA cm -2 Faradaic efficiency at constant current density.

[0039] Figure 18 c-IrO x -Faraday efficiency of MoO3 / Ti at different current densities.

[0040] Figure 19 The morphology of the catalyst after long-term stability test: (a) c-IrO x -HRSEM of MoO3 / Ti-AO; (b) c-IrO x -TEM of MoO3-AO.

[0041] Figure 20 c-IrO x -XRD patterns of MoO3 / Ti before and after long-term stability test (AO).

[0042] Figure 21 c-IrO x -Raman spectra of MoO3 / Ti before and after long-term stability test (AO).

[0043] Figure 22 c-IrO x -MoO3 / Ti O1 before and after long-term stability test (AO) S XPS spectrum.

[0044] Figure 23 c-IrO x -Mo 3d XPS spectra of MoO3 / Ti before and after long-term stability test (AO).

[0045] Figure 24 PEM electrolytic cell test: (a) Schematic diagram of PEM electrolytic cell; (b) polarization curve; (c) chronopotentiometry curve.

[0046] Figure 25 (a) c-IrO constructed based on DFT calculations X -Two atomic structure models at the MoO3 heterogeneous interface: Model I represents the O atom in MoO3 (O M ) and IrO X O vacancies in Vacancy ), Model II represents the direct interaction between O M with IrO X OM With O Vacancy Indirect interaction between the two groups; (b) 3D differential charge density diagram of Model I and Model II (left) and its corresponding 2D plane diagram (right), the yellow area represents the increase of electron density, and the blue area represents the decrease of electron density; (c) c-IrO X -MoO3-model Ⅰ, c-IrO X -MoO3- Model II and c-IrO X - Partial density of states (PDOS) of Ir 5d orbitals in model III; (d) Adsorbed oxygen intermediates in c-MoO3-IrO during OER X - Active site S in model I Ⅰ Schematic diagram of the structural evolution of the above three models; (e) Gibbs free energy changes during the OER process.

[0047] Figure 26 c-IrO constructed based on DFT calculations X Atomic structure model. DETAILED DESCRIPTION

[0048] The present invention provides an anode electrocatalytic material for hydrogen production by electrolysis of water, a preparation method thereof, and an application thereof. To make the objectives, technical solutions, and effects of the present invention more clear and explicit, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0049] The present invention provides a method for preparing an electrocatalytic material for producing hydrogen by electrolysis of water. Figure 1 As shown, it includes the following steps: S10, providing a titanium substrate with a surface rich in microporous structure; S20, preparing a molybdenum oxide precursor on the titanium substrate by a constant potential deposition method in a three-electrode system to obtain a MoO3 / Ti material; S30, mixing (NH4)2IrCl6 powder and citric acid powder in water to obtain an Ir precursor solution; S40, placing the MoO3 / Ti material in the Ir precursor solution, immersing it at room temperature for 20-40 minutes and then drying it, and finally heating it for pyrolysis to obtain the target product c-IrOx-MoO3 / Ti, that is, the anode electrocatalytic material for hydrogen production by electrolysis of water.

[0050] In this example, a nano-iridium oxide-molybdenum trioxide heterocomposite was successfully constructed on a chemically etched titanium substrate by a constant potential deposition method combined with a citric acid-assisted impregnation-pyrolysis method. A series of morphological and structural characterization techniques and DFT calculations were used to deeply analyze the morphological control effect of citric acid on MoO3 and the electronic regulation mechanism of MoO3. The prepared electrocatalytic material showed excellent OER activity (10 mA cm-2) in 0.5 M H2SO4 electrolyte. -2The overpotential is only 200mV) and the long-term stability (50mA cm -2 It can run stably for more than 130 hours under normal conditions).

[0051] Specifically, this embodiment in situ constructed a highly dispersed IrO attached to a three-dimensional staggered MoO3 sheet on a Ti substrate. x Nanoparticles (c-IrO x -MoO3 / Ti), the heterogeneous electrocatalytic material has an extremely low Ir content (Ir loading is ~28.35μg Ir cm -2 , or c-IrO x -MoO3 catalytic layer with Ir content less than 6 wt.%), high acidic OER activity (10 mA cm -2 The overpotential at 200 mV) and good long-term stability (100 mA cm -2 This special three-dimensional staggered MoO3 sheet structure induced by citric acid effectively promotes the formation of IrO x The particles are highly dispersed. DFT calculations show that IrO x -The electronic regulation at the MoO3 heterointerface may be through O M -O Vacancy This electronic regulation optimizes the adsorption energy of the active Ir sites of the catalyst to oxygen intermediates. x The dual role of morphology control and electronic regulation provides a good experimental basis and theoretical basis for designing self-supporting Ti electrodes with extremely low Ir content for acidic water oxidation. The self-assembled PEM single cell test further verifies the c-IrO x -MoO3 / Ti electrocatalysts have great application potential in renewable energy storage and conversion systems.

[0052] In some embodiments, the preparation of the titanium substrate with a surface rich in microporous structure includes: immersing the titanium mesh in an oxalic acid solution and chemically etching it at 80-100°C for 40-80 minutes; placing the etched titanium mesh in deionized water and ultrasonically cleaning it to obtain a titanium substrate with a surface rich in microporous structure. In this embodiment, roughening the surface of the titanium mesh is an important step in enhancing the adhesion strength of the surface catalytic layer on the titanium substrate. As an example, a commercially available titanium mesh is cut into small pieces of 15mm×10mm×0.2mm in size, placed in appropriate amounts of acetone and anhydrous ethanol in sequence and ultrasonically treated for 10 minutes, and then rinsed several times with appropriate amounts of deionized water. Subsequently, the cleaned titanium mesh is immersed in 50mL of 10% H2C2O4 solution and chemically etched at 90°C for 60 minutes. Finally, it is placed in 150mL of deionized water and ultrasonically cleaned for 10 minutes to obtain a titanium substrate (Ti) with a surface rich in microporous structure.

[0053] In some embodiments, in a three-electrode system, a molybdenum oxide precursor is prepared on the titanium substrate by a constant potential deposition method, and the steps of preparing the MoO3 / Ti material include: using the titanium substrate as a working electrode, Hg / Hg2SO4 as a reference electrode, a platinum sheet as a counter electrode, and a mixed solution of (NH4)2MoO4 and H2SO4 as an electrodeposition solution, and performing electrodeposition at a constant potential of -0.8V (vs.RHE); placing the titanium substrate after electrodeposition in a muffle furnace for heat treatment to obtain the MoO3 / Ti material. In this embodiment, the electrodeposition time can be 100-300s. For example, when the electrodeposition time is 100s, 200s, and 300s, respectively, the corresponding MoO3 / Ti materials are represented by MoO3 / Ti-100, MoO3 / Ti-200, and MoO3 / Ti-300, respectively. In this embodiment, the heat treatment temperature is 300-500°C, the time is 4-6h, and the heating rate is 10°C min -1 For example, the heat treatment temperature can be 300°C, 400°C, 500°C, etc., and the time can be 4h, 5h, 6h, etc.

[0054] In some embodiments, the MoO3 / Ti material is placed in the Ir precursor solution, immersed at room temperature for 20-40 minutes and then dried, and finally heated for pyrolysis. The drying temperature is 60-100°C and the time is 4-6 minutes; the pyrolysis temperature is 350-450°C and the time is 1-3 hours. In this embodiment, the drying temperature can be 60°C, 80°C, 100°C, etc., and the drying time can be 4 minutes, 5 minutes, 6 minutes, etc.; the pyrolysis temperature can be 350°C, 400°C, 450°C, etc., and the pyrolysis time can be 1 hour, 2 hours,

[0055] 3h, etc.

[0056] In some embodiments, anode electrocatalytic material for producing hydrogen by electrolysis of water is also provided, wherein the material is prepared using the method for preparing anode electrocatalytic material for producing hydrogen by electrolysis of water according to the present invention.

[0057] In some embodiments, an application of an anode electrocatalytic material for producing hydrogen by electrolysis of water is also provided, wherein the anode electrocatalytic material for producing hydrogen by electrolysis of water according to the present invention is used for producing hydrogen by electrolysis of water.

[0058] The present invention will be further explained below by means of specific embodiments:

[0059] Example 1

[0060] The preparation of c-IrOx-MoO3 / Ti includes the following steps:

[0061] 1. Pretreatment of titanium mesh:

[0062] Roughening the titanium mesh surface is an important step in enhancing the adhesion strength of the surface catalytic layer on the titanium substrate. Commercially available titanium mesh was cut into small pieces measuring 15 mm × 10 mm × 0.2 mm. These were then ultrasonically treated in appropriate amounts of acetone and anhydrous ethanol for 10 minutes, followed by several rinses with appropriate amounts of deionized water. Subsequently, the cleaned titanium mesh was immersed in 50 mL of a 10% H2C2O4 solution and chemically etched at 90°C for 60 minutes. Finally, the mesh was ultrasonically cleaned in 150 mL of deionized water for 10 minutes to obtain a titanium substrate with a surface rich in microporous structure.

[0063] 2. Preparation of MoO3 / Ti:

[0064] In a three-electrode system, a molybdenum oxide precursor was prepared on a titanium substrate by constant potential deposition. Specifically, the pretreated titanium mesh (Ti) was used as the working electrode, Hg / Hg2SO4 as the reference electrode, the platinum sheet as the counter electrode, and a mixture of 0.01M (NH4)2MoO4 and 0.002M H2SO4 as the electrodeposition solution. Electrodeposition was performed at a constant potential of -0.8V (vs. RHE), and the deposition time was 100s, 200s, and 300s, respectively. The titanium mesh after electrodeposition was then placed in a muffle furnace at 400°C for heat treatment for 5h, with a heating rate of 10°C min -1 , and finally MoO3 / Ti was obtained (MoO3 / Ti-100, MoO3 / Ti-200, and MoO3 / Ti-300 represent the corresponding products when the electrodeposition time is 100s, 200s, and 300s, respectively, and MoO3 / Ti-100, MoO3 / Ti-200, and MoO3 / Ti-300 represent the MoO3 / Ti composite materials obtained when the electrodeposition time is 100s, 200s, and 300s, respectively);

[0065] 3. Preparation of c-IrOx-MoO3 / Ti:

[0066] 11 mg of (NH4)2IrCl6 powder and 48 mg of C6H8O7 (citric acid) powder were weighed separately, mixed in 5 mL of water, and ultrasonically assisted to dissolve. The molar ratio of (NH4)2IrCl6 and C6H8O7 was 1:10. A 0.005 M Ir precursor solution was prepared and then stirred at room temperature for 24 h. MoO3 / Ti was placed in the Ir precursor solution and immersed at room temperature for 30 min. After drying at 80 ° C for 5 min, it was pyrolyzed at 400 ° C for 2 h, with a heating rate of 10 ° C min -1 The target product c-IrOx-MoO3 / Ti was finally obtained. The preparation process of IrOx-MoO3 / Ti and c-MoO3 / Ti was similar to that of c-IrOx-MoO3 / Ti-200, but without adding citric acid or Ir precursor.

[0067] 4. Preparation of c-IrOx / Ti:

[0068] Weigh 11 mg of (NH4)2IrCl6 powder and 48 mg of C6H8O7 (citric acid) powder, mix them in 5 mL of water, and dissolve them with ultrasound assistance. The molar ratio of (NH4)2IrCl6 and C6H8O7 is 1:10, and a 0.005 M noble metal Ir precursor solution is prepared. Then stir at room temperature for 24 hours. The etched titanium mesh is directly placed in the Ir precursor solution, immersed at room temperature for 30 minutes, dried at 80 ° C for 5 minutes, and pyrolyzed at 400 ° C for 2 hours, with a heating rate of 10 ° C min -1 , and finally c-IrOx / Ti was obtained. The preparation process of IrOx / Ti was similar to that of c-IrOx / Ti, but without adding citric acid.

[0069] Experimental results:

[0070] 1. Sample material characterization:

[0071] The micromorphology of the samples was observed using a high-resolution scanning electron microscope (HRSEM, Thermo APREO S) at a probe current of 13 pA and an accelerating voltage of 2 kV. X-ray diffraction (XRD) data of the samples were obtained using a desktop X-ray diffractometer (RIGAKU Smartlab) for phase structure analysis. A micro-Raman spectrometer (Renishaw in Via reflex) was used at an excitation wavelength of 532 nm and a wavelength range of 1200–100 cm -1 The Raman signal of the sample is collected within the range.

[0072] like Figure 2As shown in the figure, a nano-iridium oxide-molybdenum trioxide heterocomposite (c-IrO) was successfully constructed on a chemically etched titanium substrate by constant potential deposition combined with citric acid-assisted impregnation-pyrolysis method. x -MoO3 / Ti). Before oxalic acid etching, the titanium mesh showed a smooth surface. After etching, the surface formed a distinct porous structure. This surface roughening treatment is conducive to enhancing the bonding strength between the substrate and the catalyst layer. In the subsequent constant potential deposition process, by controlling the electrodeposition time, a series of c-IrO with different Ir / Mo mass ratios were finally formed. x Table 1 lists in detail the mass concentrations of Ir or (and) Mo in the corresponding products at different electrodeposition times obtained based on ICP-OES measurements.

[0073] Table 1 Mass concentration of Ir or (and) Mo in the corresponding products at different electrodeposition times obtained based on ICP-OES measurement

[0074]

[0075] As the electrodeposition time increases, the Mo content in the product gradually increases. However, the Ir content in the catalysts obtained after treatment with the same concentration of Ir precursor solution is basically the same, indicating that the Mo loading on the titanium substrate has no significant effect on the Ir impregnation amount. It is worth noting that the prepared catalysts all showed an ultra-low Ir loading (less than 35 μg cm -2 ), catalytic layer (c-IrO x -MoO3) does not exceed 6% by mass. In order to understand the physicochemical properties of this type of catalyst in depth, the best performance of c-IrO in electrochemical tests was selected. x -MoO3 / Ti-200(~28.35μg Ir / cm 2 ) is used as a representative for in-depth analysis. In the following, c-IrO x -MoO3 / Ti to refer to c-IrO x -MoO3 / Ti-200, the corresponding MoO3 / Ti-200 is abbreviated as MoO3 / Ti.

[0076] c-IrO x -The XRD patterns of MoO3 / Ti and MoO3 / Ti show that the two phase structures in the samples belong to MoO3(PDF#76-1003) and Ti(PDF#44-1294) respectively. Figure 3 (as shown in a). Figure 4 As the electrodeposition time increases, the XRD signal of MoO3 gradually increases, which is consistent with the change of Mo content in Table 1. However, after the subsequent impregnation-pyrolysis stage, no MoO3x -MoO3 / Ti was found to have XRD signals of iridium oxide or elemental iridium. In addition, c-IrO was directly obtained by impregnation-pyrolysis on a titanium substrate without MoO3. x No XRD signals of iridium oxide or elemental iridium were found in the / Ti. According to the ICP-OES results (Table 1), this may be related to the low Ir loading in the catalyst. Figure 5 and Figure 3 bh) for MoO3 / Ti and c-IrO x -MoO3 / Ti micromorphology and structure were characterized. Before impregnation-pyrolysis, MoO3 formed a fish-scale dense stacking layer structure on the titanium substrate. ( Figure 5 The surface material of MoO3 / Ti was further scraped for TEM analysis ( Figure 5 (as shown in cd in the figure), it was found that these dense layered structures are composed of stacked MoO3 sheets of irregular size and shape. In the high-resolution TEM field of view, three interplanar spacings of 0.326nm, 0.381nm and 0.265nm can be clearly observed, which are attributed to the (021), (110) and (111) crystal planes of MoO3, respectively, which is consistent with its XRD results. HAADF-STEM and EDS results ( Figure 5 The results (eg) show that Mo and O elements are evenly distributed on the sample surface. The Mo / O mass ratio is also close to the corresponding result calculated by S1 ( Figure 5 This means that the Mo and O elements are evenly distributed in the bulk and surface of the MoO3 layer. In addition, the MoO3 / Ti-100 and MoO3 / Ti-300 obtained with electrodeposition times of 100s and 300s, respectively, also exhibit similar fish-scale morphology characteristics ( Figure 6 As shown in Figure 2, with the extension of deposition time, the molybdenum oxide deposition layer on the titanium substrate gradually thickens and the surface becomes rough. Among them, the MoO3 / Ti-300 can be significantly observed to have an irregular fragment structure tightly packed in the fish scale-like layer, which is consistent with the TEM observation results of MoO3 / Ti. x -MoO3 / Ti exhibits completely different morphological characteristics from MoO3 / Ti. HRSEM results show that the fish-scale dense stacking layer structure on the titanium substrate surface disappears, replaced by an irregular crisscrossing sheet structure. The sheet structure surface is distributed with highly dispersed nanoparticles with a particle size of about 5-10nm, which is consistent with its TEM results ( Figure 3 In addition, the c-IrO obtained when the electrodeposition time is 100s and 300s respectively x -MoO3 / Ti-100 and c-IrOx -MoO3 / Ti-300 also showed similar morphological characteristics ( Figure 6 This special three-dimensional staggered structure of MoO3 may be conducive to the formation of nano-iridium oxide particles and the full release of their active sites. x -MoO3 / Ti high-resolution TEM field of view can be observed in two clear lattice fringes (the interplanar spacing is about 0.326nm and 0.256nm) (such as Figure 3 The selected area fast Fourier transform further confirmed that it is the MoO3 (021) crystal plane and the IrO2 (101) crystal plane (as shown in e). Figure 3 In addition, diffusely distributed fuzzy areas can be observed around these clear lattice fringes, which means that amorphous iridium oxide may exist in the structure (such as Figure 3 c-IrO x -HAADF-STEM and EDS results of MoO3 / Ti ( Figure 5 fg) further show that Mo, O, and Ir elements are evenly distributed on the sample surface. It is worth noting that c-IrO x The extremely low Ir content in c-MoO3 / Ti means that the catalyst has a lower raw material cost. x -MoO3 / Ti morphology changes, c-IrO without MoO3 x / Ti was further characterized. Figure 7 As shown, with c-IrO x -MoO3 / Ti has obvious differences in microstructure, c-IrO x The morphology of / Ti is characterized by discontinuous micron-sized flakes randomly distributed on the titanium substrate, with a large number of particles aggregated on the surface of the flakes. The thickness of the flakes is about 578nm ( Figure 7 (shown as ac in Fig. 3). c-IrO x TEM results of Ti / Figure 7 The results (de in the figure) show that these flake structures are composed of a large number of highly crystalline IrO2 and amorphous iridium oxide nanoparticles. The HAADF-STEM and EDS images further show that Ir and O are evenly distributed in the IrO2. x The above information also indirectly indicates that the presence of MoO3 is conducive to the dispersion of iridium oxide particles, but it is not enough to explain that c-IrO x -MoO3 / Ti, the high dispersion of iridium oxide particles is directly induced by MoO3, and the effect of citric acid on the morphology and structure of the catalyst needs to be investigated.

[0077] IrO x-MoO3 / Ti、IrO x / Ti (the impregnation solution contains only Ir precursor and no citric acid) and c-MoO3 / Ti (the impregnation solution contains only citric acid and no Ir precursor) were characterized.

[0078] IrO x -MoO3 / Ti、IrO x / Ti and c-MoO3 / Ti as well as the XRD results and the contents of Mo and Ir elements are respectively related to those of c-IrO x -MoO3 / Ti、c-IrO x / Ti and MoO3 / Ti are close, indicating that the addition of citric acid has no significant effect on the crystal structure or element content of the catalyst (e.g. Figure 8 As shown in Table 1). For the two groups of catalysts containing MoO3, when no citric acid was added during the impregnation stage, MoO3 maintained a fish-scale densely packed morphology on the titanium substrate, while IrO x It is attached to MoO3 in the form of agglomerated thin layers. This agglomerated iridium oxide is not conducive to the full exposure of Ir active sites ( Figure 9 After adding citric acid, c-MoO3 / Ti showed the same x -MoO3 / Ti similar structural features, that is, the tightly packed MoO3 layers are transformed into irregular flaky structures with staggered vertical and horizontal directions. The difference is that in c-IrO x Highly dispersed IrO can be observed in MoO3 / Ti x Nanoparticles are attached to the surface of these irregular sheet structures ( Figure 9 In addition, in the case of c-IrO x / Ti and IrO x Agglomerated iridium oxide sheet structures can also be observed in / Ti, although they vary in size and thickness, which may be related to the thermal decomposition of citric acid molecules ( Figure 9 c, f). It can be inferred that the morphological transformation of MoO3 promotes the x The MoO3 layer structure is connected by van der Waals force. The penetration-pyrolysis effect of citric acid molecules may interrupt the interlayer connection of MoO3 to a certain extent, resulting in the slip dislocation of MoO3 sheets, thereby mediating the dispersion of iridium oxide particles. This means that c-IrO x -MoO3 / Ti, this special heterostructure of three-dimensional interlaced MoO3 sheets loaded with nano-iridium oxide particles is the result of the joint regulation of MoO3 and citric acid.

[0079] By Raman spectroscopy ( Figure 10 (shown in a) for MoO3 / Ti, c-IrOx -MoO3 / Ti and c-IrO x / Ti structure was characterized. P can be clearly observed in the Raman spectrum of MoO3 / Ti. Ⅰ (~820cm -1 ) and P Ⅱ (~995cm -1 ) are attributed to the stretching vibration of the Mo-O bond in MoO3, which is consistent with its XRD and TEM characterization results. x There are two strong peaks in the Raman spectrum of / Ti, corresponding to E in rutile IrO2 g (~550cm -1 ) and B 2g (~720cm -1 ) are attributed to the stretching vibration of the Ir-O bond in IrO2. It is worth noting that there are two weak broad peaks observed on the left side of these two characteristic peaks, including the α peak (~450cm -1 ) and β peak (~605cm -1 ), also attributed to the stretching vibration of the Ir-O bond, but different from the amorphous IrO x (OH) y -OH association

[67] The above results show that c-IrO x Iridium oxide in / Ti is mainly rutile phase IrO2, mixed with a small amount of amorphous iridium oxide, which confirms its TEM inference. x Six peaks can be clearly observed in the Raman spectrum of -MoO3 / Ti, namely IrO x (OH) y The α peak and β peak of rutile IrO2 g and B 2g Characteristic peaks, and P of MoO3 Ⅰ and P Ⅱ Characteristic peaks, indicating c-IrO x -Iridium oxide in MoO3 / Ti also contains amorphous IrO x (OH) y and rutile phase IrO2, which further confirms the speculation based on TEM. x / Ti, the α peak is red-shifted (about 30 cm -1 ), indicating that the polarization environment of the Ir-O bond has changed, which may be related to MoO3. In addition, XPS analysis of MoO3 / Ti, c-IrO x -MoO3 / Ti and c-IrO x / Ti element valence state was analyzed to further characterize the electronic structure of the compound. Figure 10 As shown in b, c-IrO x -MoO3 / Ti has three O1s signal peaks, located at 529.91eV, 530.55eV, and 532.17eV, which belong to lattice O, defective O, and hydroxyl O, respectively. [63-64] In contrast, c-IrO x The O1s peak binding energy of lattice O in -MoO3 / Ti is slightly lower than that of MoO3 / Ti (530.26 eV) and slightly higher than that of c-IrO x / Ti(529.63eV), which means MoO3 and IrO x There may be some weak bonding between them. In addition, relative to c-IrO x / Ti (about 22%), c-IrO x -The content of defective O in MoO3 / Ti is significantly increased (~40%). The defective O in the catalyst mainly comes from amorphous IrO x (OH) y For acidic water oxidation, a higher defective O content means a higher oxygen vacancy concentration and more active adsorption sites of the catalyst. x -MoO3 / Ti high-resolution Mo 3d XPS spectrum shows that there are four signal peaks, including Mo 6+ 3d 5 / 2 (~233.17eV), Mo 6+ 3d 3 / 2 (~236.29eV), Mo 5+ 3d 5 / 2 (~232.01eV) and Mo 5+ 3d 3 / 2 (~235.10eV), among which Mo 5+ / Mo 6+ The content ratio is about 0.14( Figure 10 Compared with MoO3 / Ti, c-IrO x -MoO3 / Ti Mo 6+ The 3d peak shifts negatively (Mo +6 3d 5 / 2 and 3D 3 / 2 The peaks shifted to the low binding energy direction by 0.18eV and 0.19eV, respectively, and the Mo 5+ / Mo 6+ The content ratio increased slightly by 0.01, but Mo 5+ The 3d peak shift did not change significantly. x -High-resolution Ir 4f XPS spectrum of MoO3 / Ti ( Figure 10 As shown in (d) further reveals that, with c-IrO x / Ti, derived from amorphous IrO x (OH) y Ir 3+ 4f 7 / 2 (61.68 eV) and Ir 3+ 4f 5 / 2 (64.68eV) all shifted 0.08eV toward the high binding energy direction. 3+ / Ir 4+ The ratio increases from 0.08 to 2.70, but the Ir from rutile phase IrO2 4+ 4f 7 / 2 (62.83 eV) and Ir 4+ 4f 5 / 2 (65.93eV) did not move significantly. The above phenomenon further proves that MoO3 and IrO x There is an interaction between electrons.

[0080] 2. Electrochemical performance test:

[0081] All electrochemical tests were performed using a Chenhua 760E electrochemical workstation. The electrochemical performance of the catalyst was studied using a three-electrode system, where the working electrode was c-IrO x -MoO3 / Ti (electrode sheet exposed area 1cm 2 ), the reference electrode is Hg / Hg2SO4 electrode, and the counter electrode is platinum. The preparation process of IrO2 / Ti electrode is as follows: 2 mg of IrO2 powder is added to a mixture of 1.9 mL of ethanol and 0.1 mL of commercial Nafion solution (5 wt%) (volume ratio is 19:1). After ultrasonication, a uniform dispersion with a concentration of 1 mg mL -1 1 mL of catalyst ink was sprayed onto the surface of the chemically etched titanium mesh. The electrode was then vacuum dried at 60°C for 10 min. The catalyst loading in the obtained electrode was 0.85 mg. Ir cm -2 .

[0082] The OER performance of the catalyst was evaluated in 0.5 M H2SO4 solution. The measured electrode potential was converted to the electrode potential relative to RHE based on the calibrated Hg / Hg2SO4 reference electrode (e.g. Figure 11 As shown in Figure 2). Commercial IrO2 catalyst was selected as the benchmark for evaluating OER performance. x -MoO3 / Ti at 10 mA cm -2 The OER overpotential at 200 mV is significantly lower than that of the control sample c-IrO. x / Ti (~340mV) and commercial IrO2 (390mV) at the same current density (e.g. Figure 12 More importantly, c-IrO x -MoO3 / Ti only needs 290mV overpotential to achieve a high current density (100mA cm -2 ), while c-IrO x / Ti and commercial IrO2 catalysts require an overpotential of more than 500 mV. In addition, IrO2 prepared without adding citric acid during the impregnation stage x -MoO3 / Ti and IrO x / Ti catalyst at 10 mA cm -2 The overpotentials at the catalysts are 255mV and 360mV, respectively, which are higher than those of their corresponding citric acid-assisted pyrolysis products. The electrochemical kinetics of the catalysts were studied by Tafel curves. The lower the Tafel slope, the faster the electrochemical reaction kinetics. x / Ti(63.7mV / dec),IrO x -MoO3 / Ti(62.7mV / dec),IrO x Compared with the Tafel slope of / Ti (84.7mV / dec) and commercial IrO2 (84.8mV / dec), c-IrO x -MoO3 / Ti has the lowest Tafel slope of 58.6mV / dec. In addition, c-IrO x -The double layer capacitance of MoO3 / Ti is 20mF cm -2 Around, far exceeding IrO x -MoO3 / Ti(9.43mF cm -2 ), c-IrO x / Ti(3.71mF cm -2 ), IrO x / Ti(3.29mF cm -2 ) and commercial IrO2 (1.23 mF cm -2 )(like Figure 12 (as shown in c), indicating that the morphology regulation of MoO3 assisted by citric acid effectively promoted the x The exposure of active sites in c-MoO3 / Ti forms a higher electrochemically active surface area (ECSA). The mass activity of the catalyst is one of the important parameters for evaluating the intrinsic activity of the catalyst, so as to eliminate the interference of geometric effects on the evaluation of catalyst activity. Under the low voltage condition of 1.5V (vs.RHE), c-IrO x -MoO3 / Ti showed a high performance of 2.45A mg Ir -1The high-quality activity has surpassed most of the excellent iridium-based catalysts reported in the literature ( Figure 12 (shown in d), while c-IrO x -MoO3 / Ti at 10 mA cm -2 The OER overpotential at 1.6 V (vs. RHE) is also superior to that of the above-mentioned catalysts. The charge transfer characteristics of each catalyst at 1.6 V (vs. RHE) were further studied by electrochemical impedance spectroscopy. Figure 12 As shown in Figure e, it is obvious that compared with pure titanium electrode, titanium electrode loaded with single iridium oxide or single MoO3, c-IrO x -MoO3 / Ti and IrO x -MoO3 / Ti has lower charge transfer resistance (R ct , less than 3Ωcm -2 ) and ohmic resistance (R u , less than 0.5Ωcm -2 ). Excluding the effect of solution resistance (because EIS tests were performed in the same electrolyte), the difference in ohmic impedance may be related to the surface oxidation of the titanium substrate, but for c-IrO x / Ti、IrO x / Ti, MoO3 / Ti and pure Ti, this part of the impedance value contributes less to its overall impedance value, so the morphology and electronic structure of the catalytic layer are the key factors affecting the charge transfer impedance of the electrode itself.

[0083] In order to further explore the effect of different Ir / Mo mass ratios on the OER activity of the catalyst, the electrochemical performance of the catalysts prepared at different electrodeposition times was compared. When the electrodeposition time was 100s, 200s, and 300s, the corresponding catalyst c-IrO x -MoO3 / Ti-100, c-IrO x -MoO3 / Ti-200 and c-IrO x The Ir / Mo mass ratios of -MoO3 / Ti-300 are 0.06, 0.04, and 0.02, respectively (Table 1). Obviously, with the increase of Ir / Mo mass ratio, the three catalysts have the highest thermal conductivity at 10 mA cm -2 The overpotential at the position shows a trend of decreasing first and then increasing. When the Ir / Mo mass ratio is 0.04 (c-IrO x -MoO3 / Ti-200), the overpotential of the catalyst reaches the lowest (~200mV) ( Figure 13 The Tafel slope and charge transfer impedance also show similar characteristics, while the double layer capacitance shows the opposite trend (as shown in Figure 14-16The above results further reveal that the Ir / Mo mass ratio also has a certain influence on the activity of the catalyst. Under the experimental conditions, the catalyst c-IrO prepared when the Ir / Mo mass ratio is 0.04 x -MoO3 / Ti-200 showed the best performance.

[0084] The stability of the catalyst during the catalytic process is another important indicator for evaluating its performance. x -MoO3 / Ti can still maintain a polarization trend close to the original LSV curve after 2000 cycles of CV scanning, while c-IrO x There is a significant difference in the LSV curves of / Ti and IrO2 obtained under the same conditions. In addition, the stability of each catalyst was evaluated by chronopotentiometry. -2 Under constant current density, after 130h of continuous catalysis, c-IrO x -MoO3 / Ti overpotential increase is less than 45mV even at 100mA cm -2 Even when running at high current density, its stability can still be maintained for more than 130 hours ( Figure 12 However, the control sample c-IrO x / Ti at 10 mA cm -2 After 32 hours of continuous operation, the overpotential increase has reached more than 120mV, while commercial IrO2 only shows an overpotential increase of more than 120mV after 2 hours. x -MoO3 / Ti at 50 mA cm -2 The actual amount of oxygen produced at a constant current density is almost close to the theoretical value ( Figure 17 As shown in Figure 2, the Faradaic efficiency of the catalyst for oxygen evolution is close to 100%. More strikingly, c-IrO x -MoO3 / Ti at a higher current density (100 mA cm -2 , 200mA cm -2 )'s Faraday efficiency is also close to 100% ( Figure 18 As shown), this means that c-IrO x -MoO3 / Ti has a robust catalytic oxygen evolution ability in 0.5M H2SO4 solution.

[0085] To further study c-IrO x -MoO3 / Ti at 10 mA cm -2 The structural stability of c-IrO was tested under constant current density for 130h. x -MoO3 / Ti-AO (represents c-IrO after stability test x-MoO3 / Ti) was characterized. x -MoO3 / Ti-AO showed almost similar HRSEM, TEM and XRD characteristics ( Figure 19-20 As shown). ICP-OES results suggest that, compared with the original c-IrO x -MoO3 / Ti compared to c-IrO x In -MoO3 / Ti-AO, the Ir content decreased by 9.2%, while the mass concentration of Mo was 689.5 μg cm -2 Compared with before the test, the Mo content decreased by 2.3%, indicating that the loss of catalyst components during the long-term test was extremely low. x -MoO3 / Ti-AO, the Raman signal intensity of iridium oxide did not change significantly, but IrO x (OH) y The α peak is slightly red-shifted ( Figure 21 This suggests that the chemical environment of the Ir-O bond associated with -OH has changed slightly, which may be related to the formation of hydrogen bonds. x -MoO3 / Ti-AO O1s XPS signal peak intensity changes, the defective O content decreases slightly (~3%), and the hydroxyl O content increases slightly (~5%) ( Figure 22 shown). Mo 6+ 3d 5 / 2 The signal peak position shifts to the low binding energy direction by 0.13 eV, Mo 6+ 3d 3 / 2 The signal peak shifts negatively by 0.11 eV, but Mo 5+ / Mo 6+ The content ratio is still close to 0.14, and Mo 5+ The 3D signal peak displacement did not shift ( Figure 22 Ir 3+ The 4f signal peak position shifts toward the high binding energy direction by 0.15 eV, and the Ir 3 + / Ir 4+ Down to 2.3 ( Figure 23 The above results further indicate that the electronic structure of the catalyst has changed during the OER process, and this change is mainly related to the effect of MoO3 on IrO x electronic regulation.

[0086] c-IrO x Encouraged by the excellent catalytic activity and stability of the c-MoO3 / Ti catalyst in the acidic OER half-reaction, we attempted to assemble it into a PEM electrolysis cell for water electrolysis testing. x-MoO3 / Ti was used as the anode catalyst, while commercial Pt / C (20 wt.% Pt) was used as the cathode catalyst. Figure 24 The structure of the PEM water electrolysis device is described in detail in Figure a, where the c-IrO x -MoO3 / Ti integrated catalyst itself has a titanium mesh structure with gas diffusion function, which is conducive to simplifying the assembly process and the internal structure of PEM. x Compared with commercial IrO2, c-IrO x -MoO3 / Ti reaches 1A cm at a voltage not exceeding 1.8V -2 Industrial current intensity ( Figure 24 At the same time, at 100 mA cm -2 Even 500mA cm -2 Can run stably for more than 24 hours under high current conditions ( Figure 24 This indicates that the catalyst has great potential for practical applications.

[0087] 3. DFT calculation:

[0088] Deep understanding of MoO3-IrO by performing DFT calculations x The electronic regulation behavior between the heterogeneous interfaces and the intrinsic activity of the Ir sites on the catalyst surface. According to the phase analysis results of the catalyst and the crystal plane matching degree calculated by DFT, the MoO3 (040) crystal plane was finally selected as the calculated crystal plane of the molybdenum oxide part. According to the Raman and XPS analysis results, the amorphous IrO x It mainly contains IrO2 and IrO x (OH) y In order to simulate the real oxidation environment of the catalyst, based on the IrO2 (110) crystal structure, hydroxyl groups were introduced and oxygen vacancies were added (the ratio of hydroxyl groups to oxygen vacancies was approximately calculated based on the XPS analysis results). x The detailed calculation method is shown in the additional information. x -MoO3 / Ti, there may be two kinds of heterogeneous interface connections, one is the O atoms in MoO3 (O M ) and IrO X O vacancies in Vacancy ) direct interaction between Figure 25 Medium a model Ⅰ-O M -O Vacancy ), the other is that the O atoms in MoO3 first react with IrO X The hydroxyl H in the hydroxyl group forms a hydrogen bond, and then forms an indirect interaction with the latter O vacancy (see Figure 25 Medium a model Ⅱ-OM -HOO Vacancy ). Control sample c-IrO x / Ti's DFT calculation model (Model III) is detailed in Figure 26 In order to study the interface structure differences between Model I and Model II, the differential charge density diagrams of the two were analyzed in detail ( Figure 25 In model I, there is an obvious electron accumulation state near the Ir atoms at the interface, while O M There is an electron decay trend near the M There is a strong electronic interaction between them, and the electron transfer trend is from Ir to O M , the interfacial charge transfer trend is more obvious This electron transfer tendency is consistent with c-IrO x -MoO3 / Ti XPS analysis results are consistent. However, the interface electron distribution state in model II is opposite to that in model I. The electrons move from MoO3 to IrO x Transfer, the interface charge transfer intensity is small This means that the interfacial electronic interaction in Model II is weak. The electronic regulation behavior between heterogeneous interfaces is closely related to the d-band center theory. The closer the d-band center of the active metal site is to the Fermi level, the stronger the interaction between the active site and the reaction intermediate.

[70] However, according to the Sabatier principle, the optimal surface-interface catalytic reaction state depends on the appropriate interaction strength between the active center and the adsorbed species (reaction intermediates). Too high or too low interaction strength is not conducive to the catalytic reaction. Here, the state density of the active Ir 5d orbitals of the above three models is calculated, and the results are as follows: Figure 25 As shown in c. With c-IrO x -D-band center of model III (ε d =-1.51eV), c-IrO x -MoO3- Model I (ε d =-1.26eV) and c-IrO x -MoO3- model II d-band center (ε d =-1.16eV) are all positively shifted to the Fermi level, further verifying the electronic regulation effect of MoO3 on IrOx. It is worth noting that the d-band center of model I is between model II and model III, indicating that the O M -O Vacancy The interface electronic regulation mode may be most conducive to the OER process on the catalyst surface. In order to deeply understand the water oxidation reaction on the catalyst surface in acidic medium, the active Ir sites (S Ⅰ ) during the catalytic process ( Figure 25 (shown in d). Water molecules first adsorb on the surface of the active site and then transform into adsorbed HO*, O*, HOO*, and finally O2. Each reaction step in this process is accompanied by the transfer of a proton and electron. Subsequently, the Gibbs free energy of the adsorbed oxygen intermediates in the OER process of the three established models was compared in detail ( Figure 25 (as shown in Figure e) to further explore the reasons for the change in the intrinsic activity of the catalyst. Figure 25 e, for c-IrO x -MoO3- model I, the potential determining step (PDS) is O*→HOO*+H + +e - , the calculated theoretical overpotential is 0.907 V, while for c-IrO x -MoO3- Model II and c-IrO x -Model III, PDS are all HOO*→O2+H + +e - The calculated theoretical overpotentials are 1.201V and 1.449V respectively. This means that MoO3 has a strong effect on IrO x The electronic regulation behavior of model I optimizes the adsorption energy of oxygen intermediates on the catalyst surface; at the same time, the theoretical overpotential of model I is closer to the experimental value (~0.2V). Combined with the differential charge density and state density analysis results of model I and model II, it is believed that model I can better reflect the adsorption of IrO x The electronic regulation behavior between O and MoO3, that is, the interface electronic regulation between the two may be mainly based on M -O Vacancy Path implementation. M -O Vacancy Acts on stabilizing amorphous IrO x The electronic structure of active oxygen vacancies in the catalyst plays an important role in optimizing the catalytic activity and stability of the material.

[0089] In summary, the present invention successfully constructed highly dispersed nano-IrO2 supported on the surface of three-dimensional staggered MoO3 sheets on a chemically etched titanium substrate through constant potential deposition combined with citric acid-assisted impregnation-pyrolysis method. x The catalyst has an extremely low Ir content and exhibits high catalytic activity and long-lasting stability in the acidic water oxidation reaction. The three-dimensional staggered MoO3 sheet structure assisted by citric acid induces the IrO x The nanoparticles are highly dispersed. In addition, Raman and XPS spectroscopy studies revealed that MoO3-IrO x There is electronic interaction between heterogeneous interfaces. DFT calculations further reveal that MoO3 has a strong effect on IrO xThe electronic regulation is mainly through O M -O Vacancy The electronic regulation between the heterogeneous interfaces optimizes the adsorption energy of the active Ir sites to oxygen intermediates in the OER process. This work provides a good experimental basis and theoretical support for the design of self-supporting low iridium content titanium electrodes and their application in acidic water oxidation. x -MoO3 / Ti self-supporting catalysts also show great application potential in renewable energy storage and conversion systems.

[0090] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing an anode electrocatalytic material for hydrogen production by electrolysis of water, characterized in that: Including steps: Providing a titanium substrate with a surface rich in microporous structure; In a three-electrode system, a molybdenum oxide precursor is prepared on the titanium substrate by a constant potential deposition method to prepare a MoO3 / Ti material; Ir precursor solution was prepared by mixing (NH4)2IrCl6 powder and citric acid powder in water; The MoO3 / Ti material is placed in the Ir precursor solution, immersed at room temperature for 20-40 minutes and then dried, and finally heated for pyrolysis to obtain the target product c-IrOx-MoO3 / Ti, that is, the anode electrocatalytic material for hydrogen production by electrolysis of water.

2. The method for preparing the anode electrocatalytic material for hydrogen production by electrolysis of water according to claim 1, wherein: The preparation of the titanium substrate having a surface rich in microporous structure comprises: Immerse the titanium mesh in oxalic acid solution and chemically etch it at 80-100°C for 40-80 minutes; The etched titanium mesh was placed in deionized water and ultrasonically cleaned to obtain a titanium substrate with a surface rich in microporous structure.

3. The method for preparing an anode electrocatalytic material for hydrogen production by electrolysis of water according to claim 1, wherein: In a three-electrode system, a molybdenum oxide precursor is prepared on the titanium substrate by a constant potential deposition method to prepare the MoO3 / Ti material, comprising the following steps: The titanium substrate was used as a working electrode, Hg / Hg2SO4 was used as a reference electrode, a platinum sheet was used as a counter electrode, and a mixed solution of (NH4)2MoO4 and H2SO4 was used as an electrodeposition solution, and electrodeposition was performed at a constant potential of -0.8 V (vs. RHE); The electrodeposited titanium substrate is placed in a muffle furnace for heat treatment to obtain a MoO3 / Ti material.

4. The method for preparing an anode electrocatalytic material for hydrogen production by electrolysis of water according to claim 3, wherein: The electro-deposited titanium substrate is placed in a muffle furnace for heat treatment at a temperature of 300-500°C for 4-6 hours at a heating rate of 10°C / min. -1 .

5. The method for preparing an anode electrocatalytic material for hydrogen production by electrolysis of water according to claim 1, wherein: The MoO3 / Ti material is placed in the Ir precursor solution, immersed at room temperature for 20-40 minutes and then dried. Finally, the temperature is increased for pyrolysis treatment. The drying temperature is 60-100°C and the time is 4-6 minutes; the pyrolysis temperature is 350-450°C and the time is 1-3 hours.

6. An anode electrocatalytic material for hydrogen production by electrolysis of water, characterized in that: The material is prepared by the method for preparing the anode electrocatalytic material for hydrogen production by electrolysis of water according to any one of claims 1 to 5.

7. An application of an anode electrocatalytic material for hydrogen production by electrolysis of water, characterized in that: The anode electrocatalytic material for hydrogen production by electrolysis of water according to claim 6 is used for hydrogen production by electrolysis of water.

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