Preparation method and application of a bifunctional catalyst for seawater electrolysis

Abstract

The present application relates to the field of seawater electrolysis for obtaining clean energy hydrogen. In view of the low activity and poor corrosion resistance of the current seawater electrolysis catalyst, a preparation method of a P-CoZnO-Cu2SeS / foam nickel bifunctional composite catalyst with a grid structure is provided. First, the Cu2SeS active component is prepared on the foam nickel substrate by a solvothermal method, then the CoZnLDH grid structure material formed by the interlaced nanosheets is loaded on the prepared Cu2SeS / foam nickel by a hydrothermal method to obtain a CoZnLDH-Cu2SeS / foam nickel composite material, and finally the CoZnLDH-Cu2SeS / foam nickel is heat phosphorized to obtain the P-CoZnO-Cu2SeS / foam nickel bifunctional catalyst with the grid structure. The catalyst has high seawater electrolysis catalytic activity and strong corrosion resistance to chlorine ions in seawater, exhibits a bifunctional characteristic, and has excellent application prospect.

Description

Technical Field

[0001] This invention belongs to the field of clean hydrogen energy production, specifically relating to the preparation method of a bifunctional seawater electrolysis catalyst with a grid-like structure and its application in the oxygen evolution reaction and corrosion resistance of seawater electrolysis anode. Background Technology

[0002] Currently, the production of clean energy hydrogen through seawater electrolysis has become a promising field. Given the abundance of seawater resources on Earth, seawater electrolysis can alleviate freshwater shortages. Similar to freshwater electrolysis, seawater electrolysis also involves two half-reactions: hydrogen evolution at the cathode (HER) and oxygen evolution at the anode (OER). However, natural seawater contains complex components (bacteria, microorganisms, Cl-, etc.). - ,Br - Na + Mg 2+ Ca 2+ K + Seawater electrolysis for hydrogen production presents significant challenges for the catalysts used. For the cathode HER (Heat Evolution), bacteria, microorganisms, and insoluble precipitates (Mg(OH)₂, Ca(OH)₂) can cover the active sites on the cathode catalyst surface, leading to corrosion and deactivation. More importantly, the OER (Oxygen Evolution) activity and stability on the anode catalyst determine the efficiency of seawater electrolysis for hydrogen production. Furthermore, due to the high concentration of chloride ions (~0.5 M) in seawater, and the fact that the chloride evolution reaction (ClER) occurs at the anode under high electrochemical potentials, it competes with the OER and corrodes the electrode. Therefore, designing structurally stable, highly active, and corrosion-resistant HER / OER electrode catalysts is crucial for overcoming the challenges of seawater electrolysis for hydrogen production.

[0003] The high cost and poor durability of noble metal-based catalysts in seawater electrolysis limit their large-scale application. In recent years, transition metal hydroxides / oxides (TMHs / TMOs) have been used as OER / HER catalysts in seawater electrolysis due to their tunable composition, controllable electronic structure, and excellent catalytic performance. For example, patent 202110697625.8 discloses a method for preparing a three-dimensional iron-doped cobalt-molybdenum oxide composite catalyst (Fe-CoO / Co2Mo3O8 / MoO3@NF) and its application in seawater electrolysis. The obtained three-dimensional iron-doped cobalt-molybdenum oxide composite material exhibits high catalytic activity and stability for hydrogen evolution and oxygen evolution under chlorine-containing conditions, far superior to commercial Pt / C and IrO2 catalysts, and at a low preparation cost. However, most TMOs are only used as a protective layer to prevent chloride corrosion, rather than as catalytic active sites. Therefore, exploring a coating with high catalytic activity and good corrosion resistance in seawater electrolysis is urgently needed. Transition metal phosphides (TMPs) possess advantages such as low cost, high conductivity, good catalytic activity, and corrosion resistance, making them potential HER / OER catalysts for seawater electrolysis. Furthermore, P alloying and the presence of a PO protective layer can significantly improve the stability and chlorine corrosion resistance of TMPs. Patent 202110810371.6 discloses a nickel-iron phosphide ((Ni,Fe)OOH@NixP / NF) catalytic material, its preparation method, and its application in seawater electrolysis, demonstrating excellent catalytic OER activity. Although TMP catalysts have made significant progress in seawater electrolysis, research on their corrosion resistance is still quite limited. Low-cost and highly conductive copper-based chalcogenides exhibit excellent HER catalytic activity in seawater electrolysis, but to date, there are no reports on constructing copper-based chalcogenide-based TMOs and TMPs composite materials for catalyzing hydrogen evolution, oxygen evolution, and corrosion resistance in seawater electrolysis.

[0004] To address the shortcomings of existing technologies and the needs of applications in this field, this invention provides a bifunctional catalyst with a grid-like structure, P-CoZnO-Cu2SeS / NF, and its preparation method to overcome the problems of low catalytic activity and unsatisfactory corrosion resistance of existing seawater electrolysis catalysts. This catalyst exhibits high catalytic activity for hydrogen and oxygen evolution and excellent resistance to seawater corrosion in seawater electrolysis, and has broad application prospects. Summary of the Invention

[0005] This invention utilizes nickel foam as a substrate to modify the surface of Cu2SeS with a gridded cobalt-zinc bimetallic hydroxide (CoZnLDH), followed by thermal phosphating to synthesize a composite catalyst (P-CoZnO-Cu2SeS / NF) of bimetallic cobalt-zinc phosphide and oxide. The prepared gridded P-CoZnO-Cu2SeS / NF composite catalyst exhibits good conductivity, optimized electronic structure, large surface area, and fully exposed active sites, demonstrating excellent catalytic performance in seawater electrolysis. Furthermore, the P alloying of the metal and the formation of the metal oxide can prevent chloride ions from penetrating the catalytic active centers through electrostatic repulsion, improving the chlorine corrosion resistance of P-CoZnO-Cu2SeS / NF in seawater. Thus, the catalyst of this invention exhibits a dual function of providing both catalytic performance and corrosion resistance for seawater electrolysis.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] (1) Preparation of Cu2SeS / Ni foam

[0008] Nickel foam with dimensions of 3×2 cm was ultrasonically cleaned for 10 minutes each with acetone, hydrochloric acid (3M), and water to remove surface oil and oxides. 0.25 mmol of β-cyclodextrin was dissolved in 20 mL of N,N'-dimethylformamide solution, followed by 0.20 mmol of CuSO4·5H2O. The solution was then stirred until dissolved. Next, 0.10 mmol of selenium dioxide, 0.10 mmol of thiourea, and 0.48 mmol of citric acid were added sequentially to the mixture. After thorough dissolution, the prepared nickel foam was added and completely immersed in the solution. The mixture containing the nickel foam was then transferred to a 50 mL polytetrafluoroethylene reactor and subjected to a solvothermal reaction at 180 °C for 15 h. After cooling to room temperature, the nickel foam coated with the reaction product was removed from the reactor and washed with deionized water and anhydrous ethanol, respectively. Finally, it was vacuum dried at 50 °C for 12 h to obtain Cu2SeS / nickel foam.

[0009] (2) Preparation of CoZnLDH-Cu2SeS / nickel foam

[0010] 0.9 mmol of cobalt chloride hexahydrate, 0.3 mmol of zinc acetate dihydrate, and 6 mmol of urea were weighed and dissolved in a mixed solution of 18 mL of methanol and 12 mL of ultrapure water, and the solution was sonicated for 10 minutes. Then, the Cu₂SeS / nickel foam prepared in step (1) was immersed in the above solution and transferred to a 50 mL polytetrafluoroethylene (PTFE) reactor. The reactor was sealed and heated at 170 °C for 17 hours. After cooling to room temperature, the solid material was removed from the reactor, washed with deionized water and anhydrous ethanol, and then dried at room temperature to obtain CoZnLDH-Cu₂SeS / nickel foam.

[0011] In step (2) above, CoZnLDH is Zn2Co3(OH). 10 ·2H2O.

[0012] (3) Preparation of P-CoZnO-Cu2SeS / nickel foam bifunctional catalyst

[0013] The CoZnLDH-Cu2SeS / nickel foam bifunctional catalyst was thermally phosphated in a muffle furnace using a double-crucible method. First, a 30 mL crucible was placed inside a 100 mL crucible, leaving a gap between the two crucibles. The CoZnLDH-Cu2SeS / nickel foam was then placed in the 30 mL crucible, and 2–4 mmol of NaH2PO2·H2O was added to the gap between the two crucibles. The 100 mL crucible was then covered. Finally, the double crucibles were placed in a muffle furnace and thermally phosphated at 300 °C for 1 h. After cooling to room temperature, the double crucibles were removed from the muffle furnace, and the solid material was further extracted from the small crucible, washed three times with deionized water, and then vacuum dried at 60 °C for 12 h to obtain the P-CoZnO-Cu2SeS / nickel foam bifunctional catalyst.

[0014] In step (3) above, P-CoZnO is a composite of Co2P, ZnP2 and ZnCo2O4, and P-CoZnO is a grid-like structure formed by interlaced nanosheets and uniformly covered on Cu2SeS / nickel foam.

[0015] (4) Application of P-CoZnO-Cu2SeS / nickel foam bifunctional catalyst in seawater electrolysis

[0016] The P-CoZnO-Cu2SeS / nickel foam bifunctional catalyst prepared according to steps (1), (2), and (3) above was applied to seawater electrolysis, and its catalytic performance was as follows: at a current density of 10 mA·cm⁻¹ -2 At that time, the oxygen evolution overpotential was 210–218 mV vs. RHE; its corrosion resistance in natural seawater was: corrosion current density was 1.65 × 10⁻⁶ mV. -4~1.72×10 - 4 A·cm -2 .

[0017] The P-CoZnO-Cu2SeS / nickel foam bifunctional catalyst of this invention is applied to seawater electrolysis. Its catalytic performance and corrosion resistance are evaluated using an electrochemical workstation. The test system uses Ag / AgCl as the reference electrode, a graphite rod as the auxiliary electrode, and the P-CoZnO-Cu2SeS / nickel foam catalyst as the working electrode. A standard electrochemical three-electrode system is used. Hydrogen evolution / oxygen evolution polarization curves and potentiodynamic corrosion polarization curves are scanned in seawater electrolyte to obtain the overpotential and corrosion current density values ​​under the corresponding current density conditions.

[0018] Compared with the prior art, the present invention has the following main advantages:

[0019] (1) The P-CoZnO-Cu2SeS / foamed nickel grid structure bifunctional catalyst of the present invention is easy to prepare, low in cost, low in equipment requirements, and easy to produce on a large scale.

[0020] (2) It does not need to be coated on the electrode and can be used directly as a self-supporting electrode, which has wide applicability.

[0021] (3) The P-CoZnO-Cu2SeS / foamed nickel composite bifunctional catalyst of the present invention has a stable structure, large specific surface area, sufficient exposure of active sites, and fast electron transfer rate, and exhibits superior catalytic effect under seawater electrolysis conditions.

[0022] (4) Through hot phosphating, the P-CoZnO grid structure formed on Cu2SeS / foam nickel contains metal phosphides, oxides and PO protective layer, which blocks the penetration of chloride ions in seawater into the catalytic active components and effectively improves corrosion resistance. Attached Figure Description

[0023] Figure 1 This is a scanning electron microscope image of the grid-structured P-CoZnO-Cu2SeS / nickel foam bifunctional catalyst prepared in Example 2.

[0024] Figure 2 These are the performance graphs of hydrogen evolution (a) and oxygen evolution (b) polarization curves of Examples 2 and Comparative Examples 1, 2, and 3 in seawater electrolysis. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and comparative examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0026] Example 1

[0027] (1) Preparation of Cu2SeS / Ni foam

[0028] Nickel foam with dimensions of 3×2 cm was ultrasonically cleaned for 10 minutes each with acetone, hydrochloric acid (3M), and water to remove surface oil and oxides. 0.25 mmol of β-cyclodextrin was dissolved in 20 mL of N,N'-dimethylformamide solution, followed by 0.20 mmol of CuSO4·5H2O. The solution was then stirred until dissolved. Next, 0.10 mmol of selenium dioxide, 0.10 mmol of thiourea, and 0.48 mmol of citric acid were added sequentially to the mixture. After thorough dissolution, the prepared nickel foam was added and completely immersed in the solution. The mixture containing the nickel foam was then transferred to a 50 mL polytetrafluoroethylene reactor and subjected to a solvothermal reaction at 180 °C for 15 h. After cooling to room temperature, the nickel foam coated with the reaction product was removed from the reactor and washed with deionized water and anhydrous ethanol, respectively. Finally, it was vacuum dried at 50 °C for 12 h to obtain Cu2SeS / nickel foam.

[0029] (2) Preparation of CoZnLDH-Cu2SeS / nickel foam

[0030] 0.9 mmol of cobalt chloride hexahydrate, 0.3 mmol of zinc acetate dihydrate, and 6 mmol of urea were weighed and dissolved in a mixed solution of 18 mL of methanol and 12 mL of ultrapure water, and the solution was sonicated for 10 minutes. Then, the Cu₂SeS / nickel foam prepared in step (1) was immersed in the above solution and transferred to a 50 mL polytetrafluoroethylene (PTFE) reactor. The reactor was sealed and heated at 170 °C for 17 hours. After cooling to room temperature, the solid material was removed from the reactor, washed with deionized water and anhydrous ethanol, and then dried at room temperature to obtain CoZnLDH-Cu₂SeS / nickel foam.

[0031] (3) Preparation of P-CoZnO-Cu2SeS / nickel foam bifunctional catalyst

[0032] Thermophosphating of CoZnLDH-Cu2SeS / nickel foam was performed in a muffle furnace using a double-crucible method. First, a 30 mL crucible was placed inside a 100 mL crucible, leaving a gap between the two crucibles. CoZnLDH-Cu2SeS / nickel foam was then placed in the 30 mL crucible, and 2 mmol of NaH2PO2·H2O was added to the gap between the two crucibles. The 100 mL crucible was then covered. Finally, the two crucibles were placed in a muffle furnace and heated at 300 °C for 1 h. After cooling to room temperature, the two crucibles were removed from the muffle furnace, and the solid material was further extracted from the small crucible, washed three times with deionized water, and then vacuum dried at 60 °C for 12 h to obtain the P-CoZnO-Cu2SeS / nickel foam bifunctional catalyst.

[0033] The P-CoZnO-Cu2SeS / foamed nickel bifunctional catalyst prepared in this embodiment was applied to the tests of seawater electrolytic hydrogen evolution, oxygen evolution, and corrosion resistance. The specific values ​​of oxygen evolution overpotential and corrosion current density are shown in Table 1.

[0034] Example 2

[0035] (1) Preparation of Cu2SeS / nickel foam nanosheets: prepared according to the method and conditions of step (1) in Example 1.

[0036] (2) Preparation of CoZnLDH-Cu2SeS / foamed nickel: prepared according to the method and conditions of step (2) in Example 1.

[0037] (3) Preparation of P-CoZnO-Cu2SeS / nickel foam bifunctional catalyst: Prepared according to the method and conditions of step (3) in Example 1. The only change was the addition of 3 mmol of NaH2PO2·H2O in the crucible gap.

[0038] The P-CoZnO-Cu2SeS / foamed nickel bifunctional catalyst prepared in this embodiment was applied to the tests of seawater electrolytic hydrogen evolution, oxygen evolution, and corrosion resistance. The specific values ​​of oxygen evolution overpotential and corrosion current density are shown in Table 1.

[0039] Example 3

[0040] (1) Preparation of Cu2SeS / nickel foam nanosheets: prepared according to the method and conditions of step (1) in Example 1.

[0041] (2) Preparation of CoZnLDH-Cu2SeS / foamed nickel: prepared according to the method and conditions of step (2) in Example 1.

[0042] (3) Preparation of P-CoZnO-Cu2SeS / nickel foam bifunctional catalyst: Prepared according to the method and conditions of step (3) in Example 1. The only change was the addition of 4 mmol of NaH2PO2·H2O in the crucible gap.

[0043] The P-CoZnO-Cu2SeS / foamed nickel bifunctional catalyst prepared in this embodiment was applied to the tests of seawater electrolytic hydrogen evolution, oxygen evolution, and corrosion resistance. The specific values ​​of oxygen evolution overpotential and corrosion current density are shown in Table 1.

[0044] Comparative Example 1

[0045] Pretreatment of nickel foam: Nickel foam with a length and width of 3×2cm was ultrasonically cleaned for 10 minutes with acetone, hydrochloric acid (3M) and water respectively to remove oil and oxides from its surface.

[0046] The nickel foam prepared in this comparative example was used to test the electrolytic hydrogen evolution, oxygen evolution, and corrosion resistance properties of seawater. The specific values ​​of oxygen evolution overpotential and corrosion current density are shown in Table 1.

[0047] Comparative Example 2

[0048] Preparation of Cu2SeS / nickel foam: Prepared according to the method and conditions of step (1) in Example 1.

[0049] The Cu2SeS / foamed nickel catalyst prepared in this comparative example was applied to seawater electrolytic hydrogen evolution, oxygen evolution, and corrosion resistance tests. The specific values ​​of oxygen evolution overpotential and corrosion current density are shown in Table 1.

[0050] Comparative Example 3

[0051] Preparation of CoZnLDH-Cu2SeS / nickel foam: 0.9 mmol of cobalt chloride hexahydrate, 0.3 mmol of zinc acetate dihydrate, and 6 mmol of urea were weighed and dissolved in a mixed solution of 18 mL of methanol and 12 mL of ultrapure water, and sonicated for 10 minutes. Subsequently, the Cu2SeS / nickel foam prepared in Comparative Example 2 was immersed in the above solution and then transferred to a 50 mL polytetrafluoroethylene (PTFE) reactor. The reactor was sealed and heated at 170 °C for 17 hours. After cooling to room temperature, the solid material was removed from the reactor and washed several times with deionized water and anhydrous ethanol, and then dried at room temperature to obtain CoZnLDH-Cu2SeS / nickel foam.

[0052] The CoZnLDH-Cu2SeS / foam nickel prepared in this comparative example was used to test the electrolytic hydrogen evolution, oxygen evolution, and corrosion resistance properties of seawater. The specific values ​​of oxygen evolution overpotential and corrosion current density are shown in Table 1.

[0053] As can be seen from the comparison of the data of the embodiments and comparative examples in Table 1, the P-CoZnO-Cu2SeS / foamed nickel bifunctional catalyst of the present invention exhibits excellent catalytic performance and corrosion resistance in seawater electrolysis.

[0054] Table 1. Oxygen evolution overpotential and corrosion current density in natural seawater for seawater electrolysis catalysts.

[0055]

Claims

1. A method for preparing a bifunctional catalyst for seawater electrolysis, characterized in that, Includes the following steps: (1) Preparation of Cu2SeS / nickel foam Nickel foam with dimensions of 3×2cm was ultrasonically cleaned for 10 minutes each with acetone, 3M hydrochloric acid, and water to remove surface oil and oxides. 0.25 mmol of β-cyclodextrin was weighed and dissolved in 20 mL of N,N'-dimethylformamide solution. Then, 0.20 mmol of CuSO4·5H2O was added to the solution and stirred until dissolved. Next, 0.10 mmol of selenium dioxide, 0.10 mmol of thiourea, and 0.48 mmol of citric acid were added sequentially to the mixture. After thorough dissolution, the prepared nickel foam was added and completely immersed in the solution. The mixture containing the nickel foam was then transferred to a 50 mL polytetrafluoroethylene reactor and subjected to a solvothermal reaction at 180°C for 15 h. After cooling to room temperature, the nickel foam covered with the reaction product was removed from the reactor and washed with deionized water and anhydrous ethanol, respectively. Finally, it was vacuum dried at 50°C for 12 h to obtain Cu2SeS / nickel foam. (2) Preparation of CoZnLDH-Cu2SeS / nickel foam 0.9 mmol of cobalt chloride hexahydrate, 0.3 mmol of zinc acetate dihydrate and 6 mmol of urea were weighed and dissolved in a mixed solution of 18 mL of methanol and 12 mL of ultrapure water, and ultrasonically treated for 10 minutes. Then, the Cu2SeS / foam nickel prepared in step (1) was immersed in the above solution and then transferred to a 50 mL polytetrafluoroethylene reactor. The autoclave was sealed and heated at 170 °C for 17 hours. After cooling to room temperature, the solid material was taken out from the reactor, washed with deionized water and anhydrous ethanol, and then dried at room temperature to obtain CoZnLDH-Cu2SeS / foam nickel. (3) Preparation of P-CoZnO-Cu2SeS / nickel foam bifunctional catalyst First, place a 30 mL small crucible into a 100 mL large crucible, leaving a gap between the two crucibles. Place the CoZnLDH-Cu2SeS / nickel foam prepared in step (2) into the 30 mL small crucible and add 2-4 mmol of NaH2PO2·H2O into the gap between the two crucibles. Then cover the 100 mL large crucible with its lid. Finally, place the two crucibles in a muffle furnace and perform thermal phosphating of CoZnLDH-Cu2SeS / nickel foam at 300 °C for 1 h. After cooling to room temperature, remove the two crucibles from the muffle furnace and further remove the solid material from the small crucible. Wash the material three times with deionized water and then vacuum dry it at 60 °C for 12 h to obtain the P-CoZnO-Cu2SeS / nickel foam bifunctional catalyst.

2. The method for preparing a bifunctional catalyst for seawater electrolysis according to claim 1, characterized in that, In step (2), CoZnLDH is Zn2Co3(OH). 10 ·2H2O.

3. The method for preparing a bifunctional catalyst for seawater electrolysis according to claim 1, characterized in that, In step (3), P-CoZnO is a complex of Co2P, ZnP2 and ZnCo2O4.

4. The method for preparing a bifunctional catalyst for seawater electrolysis according to claim 1, characterized in that, In step (3), P-CoZnO is a grid-like structure formed by interlaced nanosheets and is uniformly covered on Cu2SeS / nickel foam.

5. The method for preparing a bifunctional catalyst for seawater electrolysis according to claim 1, characterized in that, Its catalytic performance in seawater electrolysis is as follows: at a current density of 10 mA·cm⁻¹ -2 At that time, the oxygen evolution overpotential is 210–218 mV vs. RHE.

6. The method for preparing a bifunctional catalyst for seawater electrolysis according to claim 1, characterized in that, Applied to seawater electrolysis, its corrosion resistance in natural seawater is as follows: corrosion current density is 1.65 × 10⁻⁶. -4 ~1.72×10 -4 A·cm -2 .

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