Seawater electrolysis catalyst with molybdate passivation layer and preparation method and application thereof

Abstract

The application provides a preparation method of a seawater electrolysis catalyst with a molybdate passivation layer, comprising the steps of: loading a molybdenum-based material on a substrate to form a pre-catalyst; placing the pre-catalyst as an anode in an electrolyte to form a molybdate passivation layer on the surface of the pre-catalyst in situ through an anodic oxidation reaction, and obtaining a seawater electrolysis catalyst with a molybdate passivation layer. The molybdate passivation layer generated in situ through the anodic oxidation reaction has a chlorine ion repulsion effect, so that the seawater electrolysis catalyst has high selectivity and stability in the process of electrolyzing seawater. The application also provides a seawater electrolysis catalyst with a molybdate passivation layer and applications of the seawater electrolysis catalyst in seawater electrolysis hydrogen production reactions, alkaline electrolytic cells and alkaline anion exchange membrane devices.

Description

Technical Field

[0001] This invention relates to the field of seawater electrolysis for hydrogen production, and particularly to a seawater electrolysis catalyst with a molybdate passivation layer, its preparation method, and its application. Background Technology

[0002] Developing seawater electrolysis technology to produce green hydrogen has significant economic and social implications. However, seawater contains chloride ions up to 0.5 M. Under the influence of the anodic potential, chloride ions undergo a chloride evolution reaction (CER), which competes with the oxygen evolution reaction (OER), reducing the selectivity of the OER. Secondly, the strong binding force between chloride ions and the metal active sites of the electrocatalyst will cause corrosion of the electrocatalyst, reducing its stability. Furthermore, the high current conditions required for industrial applications will further exacerbate the decline in selectivity and stability of the electrocatalyst.

[0003] Although existing studies have employed sulfate electrolyte additives to improve the stability of seawater electrolysis, the effects have been insufficient, and sulfate ions can couple with chloride ions, promoting substrate corrosion. Furthermore, the operating current of most seawater electrolysis anode catalysts to date is below 500 mA / cm². 2 The stability test duration was less than 200 hours, resulting in low hydrogen production rates and short service life. Therefore, developing seawater electrolysis catalysts with high selectivity and high stability at high current densities is currently a key research focus and challenge in this field, and is crucial for advancing the practical application of seawater electrolysis technology. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a seawater electrolysis catalyst with a molybdate passivation layer and its preparation method, so as to improve the selectivity and stability of seawater electrolysis under high current density.

[0005] In addition, the present invention also provides the application of the above-mentioned seawater electrolysis catalyst with molybdate passivation layer in seawater electrolysis hydrogen production reaction, alkaline electrolyzer, and alkaline anion exchange membrane device.

[0006] To achieve the above objectives, the present invention provides a method for preparing a seawater electrolysis catalyst with a molybdate passivation layer, comprising the following steps:

[0007] Molybdenum-based materials are loaded onto a substrate to form a precatalyst;

[0008] The pre-catalyst is placed in the electrolyte as the anode, and an anodic oxidation reaction is used to form a molybdate passivation layer in situ on the surface of the pre-catalyst, thereby obtaining a seawater electrolysis catalyst with a molybdate passivation layer.

[0009] The present invention also provides a seawater electrolysis catalyst with a molybdate passivation layer prepared by the above preparation method.

[0010] The present invention also provides an application of the above-mentioned seawater electrolysis catalyst with molybdate passivation layer in seawater electrolysis hydrogen production reaction, alkaline electrolyzer, and alkaline anion exchange membrane device.

[0011] Compared to existing technologies, this invention first loads a molybdenum-based material onto a substrate as the anode. During the anodic oxidation reaction, the molybdenum element in the molybdenum-based material dissolves in the electrolyte as molybdate ions at the oxidation potential. Simultaneously, under the influence of the electric field between the cathode and anode, the molybdate ions migrate towards the anode and accumulate on the anode surface due to electrostatic forces and surface adsorption, thus forming a molybdate passivation layer on the surface of the pre-catalyst. During seawater electrolysis, the molybdate passivation layer enriched at the interface between the seawater electrolysis catalyst and the electrolyte repels chloride ions due to electrostatic repulsion, inhibiting the chloride evolution reaction. This results in the seawater electrolysis catalyst with the molybdate passivation layer exhibiting high selectivity and stability, achieving a selectivity of 500 mA / cm² in alkaline seawater electrolyte. 2 The catalyst operated stably at a current density for over 3000 hours, achieving a Faradaic efficiency of 100% in the oxygen evolution reaction during seawater electrolysis. Furthermore, this preparation method has the potential for large-scale production and application, contributing to the commercialization of seawater electrolysis technology. Attached Figure Description

[0012] Figure 1 This is a scanning electron microscope image of the RuMoNi precatalyst prepared in Example 1;

[0013] Figure 2 The image shows the X-ray photoelectron spectrum of the molybdenum 3d orbitals in the RuMoNi precatalyst prepared in Example 1.

[0014] Figure 3 This is a voltage-current curve of the electrochemical oxidation process performed by cyclic voltammetry in Example 1;

[0015] Figure 4 This is a transmission electron microscope image of the RuMoNi catalyst prepared in Example 1;

[0016] Figure 5 This is a scanning electron microscope image of the RuMoNi catalyst prepared in Example 1;

[0017] Figure 6 The image shows the X-ray photoelectron spectrum of the 3d orbitals of molybdenum in the RuMoNi catalyst prepared in Example 1.

[0018] Figure 7 The X-ray diffraction spectrum of the RuMoNi catalyst prepared in Example 1 is shown below.

[0019] Figure 8The image shows a comparison of the back surface, open circuit voltage, and near-surface molybdate concentration in the solution containing the RuMoNi catalyst in Example 1.

[0020] Figure 9 This is a schematic diagram illustrating the corrosion resistance principle of the RuMoNi catalyst with a molybdate passivation layer in Example 1.

[0021] Figure 10 The stability test results of the RuMoNi catalyst prepared in Example 1 in an electrolyte composed of 1.0 M KOH and seawater were obtained by the galvanostatic method.

[0022] Figure 11 The RuMoNi catalyst prepared in Example 1 was subjected to an electrolyte consisting of 1.0 M KOH and seawater at a current of 200 mA / cm². 2 The Faraday efficiency of oxygen measured by gas chromatography when operating at a high current density under stable conditions.

[0023] Figure 12 The stability test diagram of the NiMo catalyst prepared in Example 2 in an electrolyte composed of 1.0M KOH + seawater was obtained by the galvanostatic method.

[0024] Figure 13 This is a voltage-current curve of the electrochemical oxidation process performed by cyclic voltammetry in Example 3;

[0025] Figure 14 This is a voltage-current curve of the electrochemical oxidation process performed by cyclic voltammetry in Example 4;

[0026] Figure 15 The stability test results of the RuMoNi catalyst prepared in Example 4 in an electrolyte consisting of 1.0M KOH + 2.0M NaCl were obtained by the galvanostatic method.

[0027] Figure 16 The RuMoNi catalyst prepared in Example 4 achieved 1500 mA / cm² in electrolytes of 1.0 M KOH + seawater, 1.0 M KOH, and 1.0 M KOH + 0.5 M NaCl. 2 1000mA / cm 2 500mA / cm 2 100mA / cm 2 Comparison of overpotentials required for current density;

[0028] Figure 17The UV-Vis absorption spectra of the RuMoNi catalyst prepared in Example 4 after electrolysis for 100 hours in 1.0M KOH + seawater, 1.0M KOH + 0.5M NaCl solution, and 1.0M KOH + 2.0M NaCl electrolyte.

[0029] Figure 18 The stability test diagram of the alkaline anion exchange membrane electrolyzer with RuMoNi catalyst as working electrode in Example 5, obtained by constant current method in an electrolyte composed of 1.0M KOH + seawater.

[0030] Figure 19 This is a Faraday efficiency diagram of the oxygen evolution reaction in the alkaline anion exchange membrane electrolyzer with RuMoNi catalyst as the working electrode in Example 5.

[0031] Figure 20 The current density versus voltage curves were obtained by scanning voltammetry in a three-electrode system, with the electrodes described in Example 1, Comparative Example 1, and Comparative Example 2 as working electrodes, a graphite rod as a counter electrode, and Hg / HgO as a reference electrode.

[0032] Figure 21 The graphs show the electrochemical performance of alkaline anion exchange membrane electrolyzers using the RuMoNi catalyst in Example 5 and the ruthenium chloride catalyst in Comparative Example 2 as working electrodes, respectively.

[0033] Figure 22 The stability test results are obtained by constant current method using the RuMoNi catalyst in Example 1, the foamed nickel in Comparative Example 1, and the ruthenium oxide catalyst in Comparative Example 2 as working electrodes in an electrolyte composed of 1.0 M KOH + seawater. Detailed Implementation

[0034] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0035] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0036] One embodiment of the present invention provides a method for preparing a seawater electrolysis catalyst with a molybdate passivation layer, comprising the following steps:

[0037] Molybdenum-based materials are loaded onto a substrate to form a precatalyst;

[0038] The pre-catalyst is placed in the electrolyte as the anode, and an anodic oxidation reaction is used to form a molybdate passivation layer in situ on the surface of the pre-catalyst, thereby obtaining a seawater electrolysis catalyst with a molybdate passivation layer.

[0039] This invention first loads a molybdenum-based material soluble at the anodic potential onto a substrate. During the anodic oxidation reaction, the pre-catalyst acts as the anode, and the molybdenum element in the molybdenum-based material dissolves in the solution as molybdate ions at the oxidation potential. Simultaneously, under the influence of the electric field between the cathode and anode, molybdate ions migrate towards the anode due to electrostatic forces and surface adsorption, accumulating on the anode surface and forming a molybdate passivation layer on the pre-catalyst surface. The dissolution-precipitation equilibrium formed by the molybdate on the pre-catalyst surface and the molybdate ions in the electrolyte is stable, resulting in a higher corrosion potential for this molybdenum-nickel-based catalyst with a molybdate passivation layer compared to nickel-based catalysts. During seawater electrolysis, the molybdate passivation layer at the interface between the seawater electrolysis catalyst and the electrolyte repels chloride ions, thus giving the seawater electrolysis catalyst with a molybdate passivation layer high selectivity and stability. Furthermore, this preparation method can achieve large-area (≥1m) preparation. 2 Catalyst material preparation that is compatible with industrial applications.

[0040] In some embodiments, the molybdenum-based material includes one of pure molybdenum-based material, nickel-molybdenum-based material, or cobalt-molybdenum-based material. Specifically, the pure molybdenum-based material is at least one of molybdenum dioxide or molybdenum trioxide; the nickel-molybdenum-based material is at least one of a nickel-molybdenum alloy (such as MoNi4, MoNi3) or nickel molybdate; and the cobalt-molybdenum-based material is at least one of a cobalt-chromium-molybdenum alloy or cobalt molybdate.

[0041] Molybdenum-based materials can be loaded onto a substrate using conventional methods such as hydrothermal methods and co-precipitation methods. For example, a nickel foam substrate can be immersed in a mixed solution containing nickel and molybdenum salts, and a hydrothermal reaction can be carried out in a high-pressure reactor. After drying, a nickel-molybdenum-based material loaded on a nickel foam substrate is obtained, thus obtaining a pre-catalyst.

[0042] In some embodiments, the molybdenum-based material further includes the noble metal ruthenium, which may be added simultaneously during the formation of the molybdenum-based material.

[0043] Enhanced catalytic activity can be achieved with low amounts of precious metals. The addition of the precious metal ruthenium introduces active sites with high intrinsic activity and increases the number of active sites in the material. It also synergizes with the active phase in molybdenum-based materials (especially molybdenum-nickel alloys), modulating the catalytic activity of molybdenum-based materials and greatly improving the activity of the catalyst.

[0044] The solvent in the electrolyte is at least one of deionized water, simulated seawater, or seawater, and the solute in the electrolyte is at least one of potassium hydroxide or sodium hydroxide.

[0045] In some embodiments, the temperature of the anodizing reaction is 20°C-80°C, and the substrate is nickel foam or carbon paper.

[0046] In some embodiments, the anodic oxidation reaction specifically includes cyclic voltammetry, with a potential range of 1.025 V to 1.9 V, and can be carried out in a three-electrode single-cell system or a two-electrode membrane electrode electrolytic cell.

[0047] The present invention also provides a seawater electrolysis catalyst with a molybdate passivation layer prepared by the above method and its application in seawater electrolysis for hydrogen production and in corresponding electrolysis cells, such as alkaline electrolyzers and alkaline anion exchange membrane devices.

[0048] The seawater electrolysis catalyst provided in this invention, due to its molybdate passivation layer, achieves 100% selectivity in alkaline seawater electrolytes and achieves a flow rate of 500 mA / cm². 2 The current density can be maintained stably for 100-3000 hours, or even more than 3000 hours.

[0049] During application, the concentration of chloride ions in seawater can be 0.5M-2.0M. High concentration chloride ion environment or high temperature conditions are extreme conditions that can easily cause catalyst corrosion and thus catalyst failure. The seawater electrolysis catalyst provided by this invention is applicable under a wide range of chloride ion concentrations and temperature conditions.

[0050] The technical solutions of the present invention will be explained below with reference to specific embodiments and comparative examples. Those skilled in the art will understand that the following examples are only used to explain the present invention and should not be construed as limiting the present invention.

[0051] The seawater used in this application was all taken from Huizhou City, Guangdong Province, at 22.6596N, 114.5121E. Its main components were: chloride ions 17683ppm, sulfate ions 2444ppm, sodium ions 9241ppm, magnesium ions 1107ppm, and calcium ions 361ppm. Other raw materials and equipment used in the following examples and comparative examples were conventional commercially available products or source-source equipment.

[0052] Example 1

[0053] This embodiment provides a RuMoNi catalyst with a molybdate passivation layer, the preparation method of which includes the following steps:

[0054] (1) Provide a nickel foam substrate;

[0055] (2) A molybdenum-nickel alloy was formed on the surface of a nickel foam substrate by hydrothermal reaction and reduction reaction, and ruthenium chloride was added during the synthesis of the molybdenum-nickel based material. The concentration of ruthenium in the hydrothermal reaction solution was 0.5 mM, and the concentration ratio of molybdenum, nickel and ruthenium in the hydrothermal reaction solution was Mo:Ni:Ru=80:20:1, and a RuMoNi precatalyst with a size of 1cm×3cm was synthesized.

[0056] (3) The prepared RuMoNi precatalyst was cut into 1cm×1cm and placed in an electrolyte consisting of 1.0M KOH and seawater as the working electrode (i.e., anode). A graphite rod was used as the counter electrode and Hg / HgO was used as the reference electrode to form a three-electrode system in a circular glass electrolytic cell. The electrolyte and ambient temperature were room temperature 20℃.

[0057] (4) The three-electrode system was connected to an electrochemical workstation to form a complete current and voltage circuit. Relevant parameters for electrochemical testing were set, and anodic oxidation was performed using cyclic voltammetry. The potential scan range was 1.025 V to 1.525 V relative to the reversible hydrogen electrode (V vs. RHE), with 10 scan cycles and a scan rate of 5.0 mV / s. After the reaction, a molybdate passivation layer was formed in situ on the RuMoNi pre-electrode surface, yielding a RuMoNi catalyst with a molybdate passivation layer.

[0058] Figure 1 The image shown is a scanning electron microscope image of the RuMoNi precatalyst prepared in step (2) of this embodiment. Figure 1 As can be seen, the RuMoNi precatalyst is a flower-like structure composed of three-dimensional nanorods, which is grown on a nickel foam substrate. Figure 2 The X-ray photoelectron spectrum of the molybdenum 3d orbitals in this RuMoNi precatalyst is shown below. Figure 2 It can be seen that the molybdenum element in the RuMoNi precatalyst has three valence states: 0, +4, and +6, which correspond to the three molybdenum-nickel-based and molybdenum-based phases, MoNi4, MoO2, and MoO3, respectively.

[0059] Figure 3 This is a voltage-current curve of the electrochemical oxidation process performed by cyclic voltammetry in step (4) of this embodiment. From... Figure 3As can be seen from the data, during the electrochemical oxidation process, the current density achievable by the RuMoNi precatalyst as the anode at the same potential initially increases and then stabilizes with the increase of the number of scan cycles. For example, at 1.28V, the current density at this potential during the anodic process in the first scan cycle is 90mA, while in the 9th and 10th cycles it is 153mA and 154mA, respectively. The increase in current density indicates an improvement in electrode activity during the electrochemical oxidation process. This may be due to the dissolution of molybdenum from the bulk phase, which increases the electrode specific surface area and the number of active sites exposed on the electrode surface, thereby enhancing the electrochemical activity of the catalyst.

[0060] Figure 4 The image shown is a transmission electron microscope image of the RuMoNi catalyst prepared in Example 1. According to the phase analysis based on the high-resolution image, after the electrochemical oxidation process, the obtained RuMoNi catalyst does not contain the MoO2 phase and has a thin layer of nickel molybdate on its surface.

[0061] Figure 5 The image shown is a scanning electron microscope image of the RuMoNi catalyst prepared in Example 1, for comparison. Figure 1 The RuMoNi precatalyst without electrochemical oxidation process is visible. Figure 5 The RuMoNi catalyst exhibits high roughness and porosity on its surface due to the dissolution of the MoO2 phase.

[0062] Figure 6 The image shows the X-ray photoelectron spectrum of the 3d orbital of molybdenum in the RuMoNi catalyst prepared in Example 1. The results show that the molybdenum in the RuMoNi catalyst has a +6 valence, which is consistent with the valence state of molybdate. Figure 7 The image shows the X-ray diffraction spectrum of the RuMoNi catalyst, with its diffraction peaks corresponding to the phase cards of the molybdenum-nickel alloy and nickel molybdate. (Combined with...) Figure 4 The transmission electron microscopy results show that the RuMoNi catalyst has a thin layer of nickel molybdate, and the dissolution-precipitation equilibrium of nickel molybdate can stabilize the molybdate passivation layer near the catalyst surface.

[0063] Figure 8 The graph shows a comparison of molybdate concentrations near the surface of the RuMoNi catalyst in the electrolyte of Example 1 under back-bottom, open-circuit voltage, and 0.7V conditions. This result indicates that molybdate tends to accumulate on the electrode surface, and this phenomenon is more pronounced when an anodic potential is applied to the electrode in Example 1.

[0064] The RuMoNi catalyst with a molybdate passivation layer was used as the working electrode, and the electrolyte was the same as that used in the electrochemical oxidation process in step (3). A graphite rod was used as the counter electrode and Hg / HgO was used as the reference electrode. Electrochemical tests were performed. All electrochemical tests of the three-electrode system were performed on an electrochemical workstation (VMP300). The voltage was corrected to the reversible hydrogen electrode and 85% solution resistance correction was performed.

[0065] Figure 9 This is a schematic diagram illustrating the corrosion resistance principle of the RuMoNi catalyst with the passivation layer in this embodiment.

[0066] The RuMoNi catalyst was activated in a circular glass electrolytic cell or a three-electrode system, with a solution environment of 1.0M KOH + seawater and a temperature of room temperature (20℃).

[0067] Figure 10 The stability test results of the RuMoNi catalyst in an electrolyte composed of 1.0 M KOH and seawater were obtained by a galvanostatic method. The current used in the test was 500 mA / cm². 2 Test results show that this catalyst can operate at 500 mA / cm². 2 It has been operating stably for over 3000 hours under high current density, demonstrating excellent stability.

[0068] Figure 11 The RuMoNi catalyst was tested in an electrolyte consisting of 1.0 M KOH and seawater at a current of 200 mA / cm². 2 The Faraday efficiency of oxygen was measured by gas chromatography when the high current density was operating stably. After step (4) and after 50 hours of stability testing, the Faraday efficiency of the oxygen evolution reaction of the highly active molybdenum-nickel-based catalyst was around 100%, indicating that the RuMoNi catalyst exhibits high selectivity in seawater electrolysis.

[0069] Example 2

[0070] This embodiment provides a NiMo catalyst with a molybdate passivation layer, which is prepared according to the following steps:

[0071] (1) Provide a nickel foam substrate;

[0072] (2) A molybdenum-nickel alloy was formed on the surface of a nickel foam substrate through hydrothermal and reduction reactions to synthesize a NiMo precatalyst with a size of 1 cm × 3 cm. Compared with the synthesis process of Example 1, the precious metal source ruthenium chloride was not added in the synthesis process of Example 2.

[0073] (3) The obtained NiMo precatalyst was cut into 1cm×1cm and placed in an electrolyte consisting of 1M KOH and seawater as the working electrode. A graphite rod was used as the counter electrode and Hg / HgO was used as the reference electrode to form a three-electrode system in a circular glass electrolytic cell. The electrolyte and ambient temperature were room temperature 20℃.

[0074] (4) Connect the three-electrode system to the electrochemical workstation to form a complete current and voltage circuit. Set the relevant parameters for electrochemical testing. Use cyclic voltammetry with a potential scan range of 1.169V to 1.669V (relative to the reversible hydrogen electrode), 8 scan cycles, and a scan rate of 5.0mV / s. After the reaction, a molybdate passivation layer is formed in situ on the surface of the NiMo precatalyst, thus obtaining a NiMo catalyst with a molybdate passivation layer.

[0075] Figure 12 The stability test chart of the NiMo catalyst prepared in Example 2 in an electrolyte composed of 1.0 M KOH and seawater was obtained by the galvanostatic method. The current value used in the test was 500 mA / cm. 2 Test results show that the NiMo catalyst can operate at 500 mA / cm². 2 It operates stably for over 280 hours under high current density, demonstrating excellent stability.

[0076] Example 3

[0077] This embodiment provides a nickel molybdate catalyst with a molybdate passivation layer, which is prepared according to the following steps.

[0078] (1) Provide a nickel foam substrate;

[0079] (2) Nickel molybdate was formed on the surface of a nickel foam substrate by hydrothermal reaction and reduction reaction, and a nickel molybdate precatalyst with a size of 1cm×3cm was synthesized.

[0080] (3) Cut the nickel molybdate precatalyst obtained in step (1) into 1cm×1cm and place it as the working electrode in an electrolyte composed of 1.0M KOH + seawater. Use a graphite rod as the counter electrode and Hg / HgO as the reference electrode to form a three-electrode system in a circular glass electrolytic cell. The electrolyte and ambient temperature are room temperature 20℃.

[0081] (4) Connect the three-electrode system to the electrochemical workstation to form a complete current and voltage circuit. Set the relevant parameters for electrochemical testing. Use cyclic voltammetry with a potential scan range of 1.069V to 1.569V (relative to the reversible hydrogen electrode), 50 scan cycles, and a scan rate of 10.0mV / s. After the reaction, a molybdate passivation layer is formed on the surface of the nickel molybdate precatalyst, thus obtaining a nickel molybdate catalyst with a molybdate passivation layer.

[0082] Figure 13 The voltage-current curves for the electrochemical oxidation process using cyclic voltammetry in Example 3 are shown. During the electrochemical oxidation process, the current density achievable at the same potential by the electrode initially increases and then stabilizes with increasing scan cycles, reflecting the oxidation, dissolution, and stabilization of molybdenum in nickel molybdate. The nickel molybdate catalyst with a molybdate passivation layer prepared in Example 3 was used in an electrolyte consisting of 1.0 MkOH + seawater at a current of 500 mA / cm². 2 Stability tests were conducted using the galvanostatic method, and the results showed that the nickel molybdate catalyst could withstand 500 mA / cm². 2 It has been operating stably for over 100 hours at high current density without showing any activity decay, demonstrating excellent stability.

[0083] Example 4

[0084] The difference between Example 4 and Example 1 lies in the electrolyte environment during the electrochemical oxidation of the molybdenum-nickel-based catalyst. Taking an electrolyte composed of 1.0 M KOH + 2.0 M NaCl as an example, after connecting the three-electrode system composed of RuMoNi precatalyst to an electrochemical workstation, cyclic voltammetry was used in the 1.0 M KOH + 2.0 M NaCl electrolyte, with a potential scan range of 1.169 V to 1.669 V (relative to the reversible hydrogen electrode), 5 scans, and a scan rate of 5.0 mV / s. After the reaction, a molybdate passivation layer was formed in situ on the surface of the RuMoNi preelectrode, thus obtaining a RuMoNi catalyst with a molybdate passivation layer.

[0085] Figure 14 The voltage-current curves for the electrochemical oxidation process performed by cyclic voltammetry in Example 4 show that, during the electrochemical oxidation process, the current density that the electrode can achieve at the same potential increases and then stabilizes with the increase of the number of scan cycles, reflecting the oxidation, dissolution, and stabilization process of molybdenum in the molybdenum-nickel based material. Figure 15 The stability test chart for the RuMoNi catalyst with a molybdate passivation layer in Example 4, obtained by the galvanostatic method in an electrolyte composed of 1.0M KOH + 2.0M NaCl, is shown. The current value used in the test was 500 mA / cm. 2 Test results show that this RuMoNi catalyst can achieve a current of 500 mA / cm². 2 The RuMoNi catalyst exhibits excellent stability, operating stably for over 300 hours at high current densities.

[0086] Figure 16In this embodiment, the RuMoNi catalyst achieved 1500 mA / cm² in electrolytes of 1.0 M KOH + seawater, 1.0 M KOH, and 1.0 M KOH + 0.5 M NaCl. 2 1000mA / cm 2 500mA / cm 2 100mA / cm 2 The comparison chart of overpotentials required to achieve the same current density shows that the overpotentials required to achieve the same current density are similar in different electrolytes, indicating that the method of constructing the molybdate passivation layer is effective in various electrolyte environments. Figure 17 The UV-Vis absorption spectra of the RuMoNi catalyst prepared in this embodiment after electrolysis for 100 h in 1.0 M KOH + seawater, 1.0 M KOH + 0.5 M NaCl solution, and 1.0 M KOH + 2.0 M NaCl electrolyte are shown below. Figure 17 This reflects that the Faradaic efficiency of the RuMoNi catalyst remains at 100% in electrolytes of 1.0M KOH + seawater, 1.0M KOH + 0.5M NaCl, and 1.0M KOH + 2.0M NaCl.

[0087] Example 5

[0088] This embodiment provides the application of RuMoNi catalyst with molybdate passivation layer in alkaline anion exchange membrane electrolyzer. The difference from Example 1 is the configuration and assembly method of the electrolyzer.

[0089] In this embodiment, the RuMoNi catalyst with a molybdate passivation layer prepared in Example 1 was hot-pressed together with an alkaline anion exchange membrane to form a membrane electrode, which was then assembled into an alkaline anion exchange membrane electrolyzer. This electrolyzer is a two-electrode system (working electrode and counter electrode), connected to an electrochemical workstation to form a complete voltage and current loop. Cyclic voltammetry was used to electrochemically oxidize the molybdenum-nickel-based catalyst electrode, with a potential scan range of 1.0 V to 1.6 V, 10 scan cycles, and a scan rate of 5.0 mV / s.

[0090] Figure 18 The stability test graph for the alkaline anion exchange membrane electrolyzer using RuMoNi catalyst as the working electrode in Example 5, obtained by the galvanostatic method in an electrolyte composed of 1.0 M KOH + seawater, is shown. The test current value is 500 mA / cm². 2 (i.e., 0.5 A / cm²), test results show that this RuMoNi catalyst can achieve 500 mA / cm². 2 It operates stably for over 240 hours under high current density, demonstrating excellent stability.

[0091] Figure 19The figure shows the Faraday efficiency of the oxygen evolution reaction in the alkaline anion exchange membrane electrolyzer with RuMoNi catalyst as the working electrode in Example 5. The results show that the RuMoNi catalyst has 100% selectivity for the oxygen evolution reaction during electrolysis.

[0092] Comparative Example 1

[0093] Comparative Example 1 provides a blank nickel foam electrode as a reference, with a thickness of 0.5 mm.

[0094] Comparative Example 2

[0095] Comparative Example 2 uses commercially available ruthenium oxide catalyst (RuO2) as a reference, and the specific preparation process is as follows:

[0096] Commercially available ruthenium oxide powder was mixed with isopropanol to prepare a slurry, wherein the mass concentration of ruthenium oxide was 10 mg / mL. The slurry was then uniformly dispersed on 0.5 mm nickel foam, with the loading controlled at 4 mg / cm³. 2 Ruthenium oxide catalyst was obtained.

[0097] The RuMoNi catalyst with molybdate passivation layer prepared in Example 1, the blank nickel foam described in Comparative Example 1, and the ruthenium oxide catalyst in Comparative Example 2 were used as working electrodes, with a graphite rod as the counter electrode and Hg / HgO as the reference electrode. Current density versus voltage curves were obtained in the three-electrode system using scanning voltammetry. Figure 20 ).from Figure 20 As can be seen from the above, the RuMoNi catalyst with a molybdate passivation layer prepared in Example 1 can achieve 1000 mA / cm² when the electrode potential is 1.70 V relative to the reversible hydrogen electrode. 2 The current density was higher, while in Comparative Examples 1 and 2 it was only 19 mA / cm². 2 and 108 mA / cm 2 The current density obtained indicates that the RuMoNi catalyst with a nickel molybdate passivation layer has superior performance compared to conventional commercial electrodes, enabling efficient industrial-grade current density seawater hydrogen production.

[0098] The ruthenium oxide catalyst from Comparative Example 2 was assembled into an alkaline anion exchange membrane electrolyzer in the same manner as in Example 5. Figure 21 The figures show the electrochemical performance of alkaline anion exchange membrane electrolyzers with RuMoNi catalyst and ruthenium chloride catalyst as working electrodes, respectively. The tests were conducted in electrolytes consisting of 1.0 M KOH and seawater at 80 °C and 20 °C, respectively. As can be seen from the figures, the RuMoNi catalyst with molybdate passivation layer requires a lower voltage to achieve the same current density than Comparative Example 2, and has higher activity.

[0099] Figure 22 The stability test results of the RuMoNi catalyst with molybdate passivation layer prepared in Example 1, the blank nickel foam described in Comparative Example 1, and the ruthenium oxide catalyst in Comparative Example 2 were obtained by galvanostatic method in an electrolyte composed of 1.0 M KOH + seawater. The current value used in the test was 500 mA / cm. 2 .from Figure 22 As can be seen, Comparative Example 1 and Comparative Example 2 are stable only within 10h and 50h, respectively, demonstrating that the RuMoNi catalyst with nickel molybdate passivation layer in Example 1 has excellent stability.

[0100] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention should not depart from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a seawater electrolysis catalyst with a molybdate passivation layer, characterized in that, Including the following steps: Molybdenum-based materials are loaded onto a substrate to form a precatalyst; The pre-catalyst is placed in the electrolyte as the anode, and an anodic oxidation reaction is used to form a molybdate passivation layer in situ on the surface of the pre-catalyst, thereby obtaining a seawater electrolysis catalyst with a molybdate passivation layer.

2. The preparation method according to claim 1, characterized in that, The molybdenum-based material includes at least one of pure molybdenum-based material, molybdenum-nickel-based material, or molybdenum-cobalt-based material.

3. The preparation method according to claim 2, characterized in that, The pure molybdenum-based material includes at least one of molybdenum dioxide or molybdenum trioxide; the molybdenum-nickel-based material includes at least one of molybdenum-nickel alloy or nickel molybdate; the molybdenum-cobalt-based material includes at least one of cobalt-chromium-molybdenum alloy or cobalt molybdate.

4. The preparation method according to claim 1, characterized in that, The molybdenum-based material also includes the precious metal ruthenium.

5. The preparation method according to claim 1, characterized in that, The solvent in the electrolyte includes at least one of deionized water, simulated seawater, or seawater, and the solute in the electrolyte includes at least one of potassium hydroxide or sodium hydroxide.

6. The preparation method according to claim 1, characterized in that, The step "loading molybdenum-based material on a substrate" includes: The molybdenum-based material is formed on the substrate using a hydrothermal method or a co-precipitation method.

7. The preparation method according to claim 1, characterized in that, The temperature of the anodic oxidation reaction is 20℃-80℃.

8. The preparation method according to claim 1, characterized in that, The substrate is either nickel foam or carbon paper.

9. A seawater electrolysis catalyst having a molybdate passivation layer, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

10. The application of a seawater electrolysis catalyst with a molybdate passivation layer as described in claim 9 in seawater electrolysis for hydrogen production, alkaline electrolyzers, and alkaline anion exchange membrane devices.

Images