A Ni3S2 / SiNWs cathode material for efficient photoelectrocatalytic hydrogen evolution in seawater and its preparation method

Abstract

The present invention discloses a Ni3S2 / SiNWs cathode material for efficient hydrogen evolution from seawater photoelectrocatalysis and its preparation method. The silicon nanowire substrate is prepared by metal-assisted chemical etching, and then Ni3S2 nanocatalysts are grown on the silicon nanoarray through photoelectrodeposition and chemical vapor deposition processes. Compared with the traditional binary catalyst composite process, the preparation method of the present invention has stronger adhesion by directly depositing the growth promoter on the surface of the SiNWs substrate; Ni3S2 has high conductivity, which can effectively improve the charge transfer rate of silicon-based materials; the nanostructure of Ni3S2 and p-Si has a large specific surface area, which builds a large amount of H on the cathode surface. + Adsorption and water decomposition active sites, so the Ni3S2 / SiNWs cathode material has the advantages of small charge transfer resistance, multiple surface active sites and efficient hydrogen evolution in the photoelectrocatalytic seawater hydrogen evolution system.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterial preparation and photoelectrocatalytic hydrogen evolution from seawater, and in particular to a Ni3S2 / SiNWs cathode material for efficient photoelectrocatalytic hydrogen evolution from seawater and a preparation method thereof. Background Art

[0002] In recent years, rapid social development has accelerated the depletion of traditional fossil fuels, and the resulting climate and environmental damage has intensified, spurring research on abundant, environmentally safe alternative fuels. Hydrogen (H2) is widely recognized as a clean, sustainable energy carrier, boasting a high energy density of 120-142 MJ / kg per unit mass and producing only water as a combustion byproduct. Currently, large-scale H2 production still relies on pure water. Given the scarcity of freshwater resources, a growing number of researchers are turning their attention to seawater.

[0003] Compared with the use of pure water for hydrogen evolution, seawater, as one of the most abundant resources on earth, contains more inorganic salts. In the photoelectrocatalytic seawater hydrogen evolution system, it can improve the conductivity of the electrolyte, accelerate charge transfer, and increase the transmission rate of photogenerated carriers at the cathode catalyst interface, effectively promoting the hydrogen evolution performance of the catalyst. However, during the photoelectrocatalytic seawater hydrogen evolution process, H + The reduction reaction forms a local alkaline area, and the Mg in seawater 2+ , Ca 2+ Insoluble precipitates such as Mg(OH)2 and Ca(OH)2 are generated on the surface of the photocathode, which not only corrodes the cathode material, but also the occurrence of side reactions will cover the hydrogen evolution active sites on the cathode surface, thereby interfering with the H evolution reaction on the cathode surface. + The reduction reaction significantly reduces the efficiency of hydrogen evolution from the cathode catalyst. Therefore, due to the poor conductivity of most semiconductor materials, a higher applied potential is required to generate a higher current density for the catalyst, resulting in a poor efficiency in hydrogen evolution from seawater. Consequently, the development of photoelectrocatalysts in hydrogen evolution from seawater has been relatively slow.

[0004] As an abundant and ubiquitous material for photovoltaic applications, silicon (Si) has attracted widespread attention due to its promising prospects for PEC water splitting. In particular, p-type silicon (p-Si) has been widely used in photoelectrocatalysis due to its narrow bandgap (~1.12 eV), wide photoresponse range, and high photogenerated carrier mobility. However, p-Si has limitations as a hydrogen evolution photocathode due to its high hydrogen evolution overpotential, poor conductivity, easy recombination of photogenerated carriers and holes, and susceptibility to surface corrosion. Summary of the Invention

[0005] The purpose of the present invention is to provide a Ni3S2 / SiNWs cathode material for efficient hydrogen evolution in seawater photoelectrocatalysis and a preparation method thereof. The cathode material prepared thereby has the advantages of strong binding force, low charge transfer resistance, multiple surface active sites, and efficient hydrogen evolution.

[0006] In one aspect of the present invention, a method for preparing a Ni3S2 / SiNWs cathode material for efficient photoelectrocatalytic hydrogen evolution in seawater is provided. According to an embodiment of the present invention, the method comprises the following steps:

[0007] (1) A NiCl2 aqueous solution was prepared and nitrogen was passed through it for half an hour to remove oxygen. A three-electrode system was used, with a silicon nanowire substrate as the working electrode. N2 was continuously passed through the solution to prepare a Ni / SiNWs photoelectrocatalyst by photoelectrodeposition.

[0008] (2) The Ni / SiNWs catalyst and sulfur powder were placed in two areas of a vacuum tube furnace, respectively, and then heated to different temperatures. A certain flow of N2 was introduced into the tube furnace to prepare the Ni3S2 / SiNWs cathode material for efficient hydrogen evolution from seawater photoelectrocatalysis.

[0009] In addition, the method for preparing a Ni3S2 / SiNWs cathode material for efficient photoelectrocatalytic hydrogen evolution in seawater according to the above embodiment of the present invention may also have the following additional technical features:

[0010] In some embodiments of the present invention, in step (1), the method for preparing the silicon nanowire substrate comprises the following steps:

[0011] (101) The silicon wafer was ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 15–20 min in sequence. The cleaned silicon wafer was then placed in a mixed solution of sulfuric acid and hydrogen peroxide and kept at a constant temperature of 80 °C in a water bath for 30–40 min to completely remove organic matter on its surface.

[0012] (102) preparing an etching solution of a certain concentration consisting of nitric acid, ammonium fluoride, and silver nitrate, and a low-concentration and high-concentration silver removal solution consisting of nitric acid, hydrochloric acid, and deionized water;

[0013] (103) The silicon wafer is sequentially placed into the three solutions prepared in step (102) to react and obtain a silicon nanowire substrate.

[0014] In some embodiments of the present invention, in step (101), the silicon wafer is a p-type silicon wafer with single-side polishing, a resistivity of 1-10Ω·cm, a length and width of 1 cm, a thickness of 500 μm, and a volume ratio of sulfuric acid to hydrogen peroxide of 3:1.

[0015] In some embodiments of the present invention, in step (102), the etching solution concentration composition is 1.85 mol / L nitric acid, 2.0 mol / L ammonium fluoride, and 0.02 mol / L silver nitrate, the volume ratio of nitric acid, hydrochloric acid, and deionized water in the low-concentration silver removal solution is 1:1:3, and the volume ratio of nitric acid, hydrochloric acid, and deionized water in the high-concentration silver removal solution is 1:1:1.

[0016] In some embodiments of the present invention, in the step (103), the etching temperature is 26° C., the etching time is 30 min, the substrate is immersed in a low-concentration silver removal solution for 10 to 15 min, and then immersed in a high-concentration silver removal solution for 10 to 12 h.

[0017] In some embodiments of the present invention, in step (1), the concentration of the NiCl2 aqueous solution is 10.0 mmol / L, and the three-electrode system used includes a Pt electrode as a counter electrode and an Ag / AgCl electrode as a reference electrode.

[0018] In some embodiments of the present invention, in step (1), the light intensity during photoelectric deposition is 100 mW·cm -2 , the deposition voltage is -1.5V, and the deposition time is 15 to 60s.

[0019] In some embodiments of the present invention, in step (2), the vacuum degree in the tube furnace is 0.1-0.01 mBar, sulfur powder is placed in the inlet area of ​​the tube furnace, the Ni / SiNWs catalyst is placed in the middle area of ​​the tube furnace, and the Ni / SiNWs catalyst is placed vertically along the flow direction of nitrogen.

[0020] In some embodiments of the present invention, when the temperature of the intermediate zone reaches 270°C, nitrogen starts to flow in the tube, the nitrogen flow rate in the tube is 200 sccm, the inlet zone is maintained at 125°C for 30 minutes, and the intermediate zone is maintained at 300°C for 40 minutes.

[0021] In another aspect of the present invention, the present invention proposes a Ni3S2 / SiNWs cathode material prepared by the above-mentioned method for preparing Ni3S2 / SiNWs cathode material for efficient photoelectrocatalytic hydrogen evolution in seawater.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1) The present invention first uses a metal-assisted chemical etching method to prepare a silicon nanowire substrate, and then sequentially grows a transition metal sulfide Ni3S2 nanocatalyst on the silicon nanoarray through photodeposition and chemical vapor deposition processes. Compared with the traditional binary catalyst composite process, the direct deposition of the growth promoter on the surface of the SiNWs substrate has stronger adhesion; and Ni3S2 has high conductivity, which can effectively improve the charge transfer rate of silicon-based materials; the nanostructure of Ni3S2 and p-Si has a large specific surface area, and a large amount of H + Adsorption and water decomposition active sites, so the Ni3S2 / SiNWs cathode material has the advantages of strong binding force, small charge transfer resistance, multiple surface active sites, and efficient hydrogen evolution in the photoelectrocatalytic seawater hydrogen evolution system.

[0024] 2) The present invention distributes and attaches sulfur and nickel, which can effectively control the size and loading amount of nickel sulfide, and uses a chemical vapor deposition process to combine nickel sulfide with a silicon substrate. The bonding force is strong and has a great influence on the stability of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Flow chart for the preparation of Ni3S2 / SiNWs binary photoelectrocatalyst in an embodiment of the present invention;

[0026] Figure 2 The linear sweep voltammetry curve of Ni / SiNWs photoelectrocatalyst in simulated seawater in an embodiment of the present invention;

[0027] Figure 3 The linear sweep voltammetry curve of Ni3S2 / SiNWs photoelectrocatalyst in simulated seawater in an embodiment of the present invention;

[0028] Figure 4 The impedance spectrum of the Ni3S2 / SiNWs photoelectrocatalyst in simulated seawater in an embodiment of the present invention, where the abscissa is the real part and the ordinate is the imaginary part;

[0029] Figure 5 This is a stability test of the Ni3S2 / SiNWs photoelectrocatalyst at 0V vs. RHE potential in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] Example 1

[0032] A method for preparing a Ni3S2 / SiNWs cathode material for efficient photoelectrocatalytic hydrogen evolution in seawater comprises the following steps:

[0033] (1) Preparation of silicon nanowire substrate

[0034] The silicon wafer was ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 15 minutes in sequence, and then placed in a mixed solution of sulfuric acid and hydrogen peroxide with a volume ratio of 3:1, and kept at a constant temperature of 80°C in a water bath for 40 minutes to completely remove the organic matter on its surface. The silicon wafer was then ultrasonically cleaned with deionized water for 3 minutes and repeated 10 times. The silicon wafer was then immersed in an etching solution with a concentration of 1.85 mol / L nitric acid, 2.0 mol / L ammonium fluoride, and 0.02 mol / L silver nitrate, and etched for 30 minutes at a constant temperature of 26°C in a water bath. Finally, the etched silicon wafer was first soaked in a desilvering solution with a volume ratio of nitric acid, hydrochloric acid, and deionized water of 1:1:3 for 15 minutes, and then soaked in a desilvering solution with a volume ratio of nitric acid, hydrochloric acid, and deionized water of 1:1:1 for 12 hours to prepare a silicon nanowire substrate.

[0035] (2) Preparation of Ni / SiNWs photoelectrocatalysts by photodeposition

[0036] 50 ml of 10.0 mmol / L NiCl2 aqueous solution was placed in a reactor and nitrogen was passed through the solution for half an hour to remove oxygen. A three-electrode system was used with the silicon nanowire substrate as the working electrode, the Pt electrode as the counter electrode, and the Ag / AgCl electrode as the reference electrode. N2 was continuously passed through the solution at 100 mW·cm -2 Under the irradiation of strong simulated sunlight, a voltage of -1.5V was continuously applied to the working electrode for 15s to prepare the Ni / SiNWs photoelectrocatalyst.

[0037] (3) Preparation of Ni3S2 / SiNWs photoelectrocatalyst by chemical vapor deposition

[0038] The Ni / SiNWs catalyst and sulfur powder in a quartz crucible were placed in the middle zone (zone 2) and entrance zone (zone 1) of a tube furnace with a vacuum degree of 0.1-0.01 mBar, respectively. The Ni / SiNWs catalyst was placed vertically along the direction of carrier gas flow. The temperatures of the two zones were heated to 125°C (zone 1) and 300°C (zone 2) within 10 minutes. When the temperature of zone 2 reached 270°C, nitrogen gas with a flow rate of 200 sccm began to flow into the tube. Zone 1 was maintained at 125°C for 30 minutes, and zone 2 was maintained at 300°C for 40 minutes to prepare the Ni3S2 / SiNWs photoelectrocatalyst.

[0039] Example 2

[0040] A method for preparing a Ni3S2 / SiNWs cathode material for efficient photoelectrocatalytic hydrogen evolution in seawater comprises the following steps:

[0041] (1) Preparation of silicon nanowire substrate

[0042] The silicon wafer was ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 15 minutes in sequence, and then placed in a mixed solution of sulfuric acid and hydrogen peroxide with a volume ratio of 3:1, and kept at a constant temperature of 80°C in a water bath for 40 minutes to completely remove the organic matter on its surface. The silicon wafer was then ultrasonically cleaned with deionized water for 3 minutes and repeated 10 times. The silicon wafer was then immersed in an etching solution with a concentration of 1.85 mol / L nitric acid, 2.0 mol / L ammonium fluoride, and 0.02 mol / L silver nitrate, and etched for 30 minutes at a constant temperature of 26°C in a water bath. Finally, the etched silicon wafer was first soaked in a desilvering solution with a volume ratio of nitric acid, hydrochloric acid, and deionized water of 1:1:3 for 15 minutes, and then soaked in a desilvering solution with a volume ratio of nitric acid, hydrochloric acid, and deionized water of 1:1:1 for 12 hours to prepare a silicon nanowire substrate.

[0043] (2) Preparation of Ni / SiNWs photoelectrocatalysts by photodeposition

[0044] 50 ml of 10.0 mmol / L NiCl2 aqueous solution was placed in a reactor and nitrogen was passed through the solution for half an hour to remove oxygen. A three-electrode system was used with the silicon nanowire substrate as the working electrode, the Pt electrode as the counter electrode, and the Ag / AgCl electrode as the reference electrode. N2 was continuously passed through the solution at 100 mW·cm -2 Under the irradiation of strong simulated sunlight, a voltage of -1.5V was continuously applied to the working electrode for 30s to prepare the Ni / SiNWs photoelectrocatalyst.

[0045] (3) Preparation of Ni3S2 / SiNWs photoelectrocatalyst by chemical vapor deposition

[0046] The Ni / SiNWs catalyst and sulfur powder in a quartz crucible were placed in the middle zone (zone 2) and entrance zone (zone 1) of a tube furnace with a vacuum degree of 0.1-0.01 mBar, respectively. The Ni / SiNWs catalyst was placed vertically along the direction of carrier gas flow. The temperatures of the two zones were heated to 125°C (zone 1) and 300°C (zone 2) within 10 minutes. When the temperature of zone 2 reached 270°C, nitrogen gas with a flow rate of 200 sccm began to flow into the tube. Zone 1 was maintained at 125°C for 30 minutes, and zone 2 was maintained at 300°C for 40 minutes to prepare the Ni3S2 / SiNWs photoelectrocatalyst.

[0047] Example 3

[0048] A method for preparing a Ni3S2 / SiNWs cathode material for efficient photoelectrocatalytic hydrogen evolution in seawater comprises the following steps:

[0049] (1) Preparation of silicon nanowire substrate

[0050] The silicon wafer was ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 15 minutes in sequence, and then placed in a mixed solution of sulfuric acid and hydrogen peroxide with a volume ratio of 3:1, and kept at a constant temperature of 80°C in a water bath for 40 minutes to completely remove the organic matter on its surface. The silicon wafer was then ultrasonically cleaned with deionized water for 3 minutes and repeated 10 times. The silicon wafer was then immersed in an etching solution with a concentration of 1.85 mol / L nitric acid, 2.0 mol / L ammonium fluoride, and 0.02 mol / L silver nitrate, and etched for 30 minutes at a constant temperature of 26°C in a water bath. Finally, the etched silicon wafer was first soaked in a desilvering solution with a volume ratio of nitric acid, hydrochloric acid, and deionized water of 1:1:3 for 15 minutes, and then soaked in a desilvering solution with a volume ratio of nitric acid, hydrochloric acid, and deionized water of 1:1:1 for 12 hours to prepare a silicon nanowire substrate.

[0051] (2) Preparation of Ni / SiNWs photoelectrocatalysts by photodeposition

[0052] 50 ml of 10.0 mmol / L NiCl2 aqueous solution was placed in a reactor and nitrogen was passed through the solution for half an hour to remove oxygen. A three-electrode system was used with the silicon nanowire substrate as the working electrode, the Pt electrode as the counter electrode, and the Ag / AgCl electrode as the reference electrode. N2 was continuously passed through the solution at 100 mW·cm -2 Under high-intensity simulated sunlight, a voltage of -1.5 V was continuously applied to the working electrode for 45 seconds to prepare the Ni / SiNWs photoelectrocatalyst.

[0053] (3) Preparation of Ni3S2 / SiNWs photoelectrocatalyst by chemical vapor deposition

[0054] The Ni / SiNWs catalyst and sulfur powder in a quartz crucible were placed in the middle zone (zone 2) and entrance zone (zone 1) of a tube furnace with a vacuum degree of 0.1-0.01 mBar, respectively. The Ni / SiNWs catalyst was placed vertically along the direction of carrier gas flow. The temperatures of the two zones were heated to 125°C (zone 1) and 300°C (zone 2) within 10 minutes. When the temperature of zone 2 reached 270°C, nitrogen gas with a flow rate of 200 sccm began to flow into the tube. Zone 1 was maintained at 125°C for 30 minutes, and zone 2 was maintained at 300°C for 40 minutes to prepare the Ni3S2 / SiNWs photoelectrocatalyst.

[0055] Example 4

[0056] A method for preparing a Ni3S2 / SiNWs cathode material for efficient photoelectrocatalytic hydrogen evolution in seawater comprises the following steps:

[0057] (1) Preparation of silicon nanowire substrate

[0058] The silicon wafer was ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 15 minutes in sequence, and then placed in a mixed solution of sulfuric acid and hydrogen peroxide with a volume ratio of 3:1, and kept at a constant temperature of 80°C in a water bath for 40 minutes to completely remove the organic matter on its surface. The silicon wafer was then ultrasonically cleaned with deionized water for 3 minutes and repeated 10 times. The silicon wafer was then immersed in an etching solution with a concentration of 1.85 mol / L nitric acid, 2.0 mol / L ammonium fluoride, and 0.02 mol / L silver nitrate, and etched for 30 minutes at a constant temperature of 26°C in a water bath. Finally, the etched silicon wafer was first soaked in a desilvering solution with a volume ratio of nitric acid, hydrochloric acid, and deionized water of 1:1:3 for 15 minutes, and then soaked in a desilvering solution with a volume ratio of nitric acid, hydrochloric acid, and deionized water of 1:1:1 for 12 hours to prepare a silicon nanowire substrate.

[0059] (2) Preparation of Ni / SiNWs photoelectrocatalysts by photodeposition

[0060] 50 ml of 10.0 mmol / L NiCl2 aqueous solution was placed in a reactor and nitrogen was passed through the solution for half an hour to remove oxygen. A three-electrode system was used with the silicon nanowire substrate as the working electrode, the Pt electrode as the counter electrode, and the Ag / AgCl electrode as the reference electrode. N2 was continuously passed through the solution at 100 mW·cm -2 Under high-intensity simulated sunlight irradiation, a voltage of -1.5 V was continuously applied to the working electrode for 60 s to prepare the Ni / SiNWs photoelectrocatalyst.

[0061] (3) Preparation of Ni3S2 / SiNWs photoelectrocatalyst by chemical vapor deposition

[0062] The Ni / SiNWs catalyst and sulfur powder in a quartz crucible were placed in the middle zone (zone 2) and entrance zone (zone 1) of a tube furnace with a vacuum degree of 0.1-0.01 mBar, respectively. The Ni / SiNWs catalyst was placed vertically along the direction of carrier gas flow. The temperatures of the two zones were heated to 125°C (zone 1) and 300°C (zone 2) within 10 minutes. When the temperature of zone 2 reached 270°C, nitrogen gas with a flow rate of 200 sccm began to flow into the tube. Zone 1 was maintained at 125°C for 30 minutes, and zone 2 was maintained at 300°C for 40 minutes to prepare the Ni3S2 / SiNWs photoelectrocatalyst.

[0063] The prepared Ni / SiNWs photoelectrocatalyst and Ni3S2 / SiNWs photoelectrocatalyst were respectively tested for photoelectrocatalytic hydrogen evolution performance in seawater:

[0064] Hydrogen evolution tests were conducted using a CHI660D electrochemical workstation, using a 300W xenon lamp equipped with a 420nm cutoff filter to simulate sunlight. 50ml of simulated seawater was added to a three-electrode sealed electrolytic cell with Ni / SiNWs and Ni3S2 / SiNWs catalysts as working electrodes, platinum as the counter electrode, and Ag / AgCl as the reference electrode. After the circuit was connected, linear sweep voltammetry was used for hydrogen evolution testing, with a voltage range of -0.5 to 1.4V and a scan rate of 0.1V / s. The program was then started to obtain a linear sweep voltammetry (LSV) curve.

[0065] like Figure 2 As shown in Figure 2, the Ni / SiNWs catalyst produces a large photocurrent density under photoelectric conditions, indicating that the effective composite of SiNWs and Ni nanoparticles greatly improves its photoelectrocatalytic hydrogen evolution performance. Figure 3 As shown in Figure 2, Ni3S2 / SiNWs catalyst also produces a large photocurrent density under photoelectric conditions, and its photoelectrocatalytic hydrogen evolution performance is excellent. Figure 4 As shown in Figure 2, the curvature radius of the impedance arc of the Ni3S2 / SiNWs catalyst is significantly smaller than that of the SiNWs catalyst, indicating that after the Ni3S2 co-catalyst is grown on the SiNWs surface by chemical vapor deposition, the carrier transmission rate at the interface is significantly accelerated. Figure 5 As shown, under the condition of 0V vs. RHE applied potential, the photocurrent density generated by the Ni3S2 / SiNWs catalyst remains stable for a long time, indicating that the Ni3S2 / SiNWs catalyst can stably evolve hydrogen, and the chemical vapor deposition method is used to make the binding force between the co-catalyst Ni3S2 and SiNWs strong.

[0066] The above content is merely an example and explanation of the structure of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a Ni3S2 / SiNWs cathode material for efficient photoelectrocatalytic hydrogen evolution in seawater, characterized in that: The following steps are involved: (1) A NiCl2 aqueous solution was prepared and nitrogen was passed through it for half an hour to remove oxygen. A three-electrode system was used, with the silicon nanowire substrate as the working electrode. N2 was continuously passed through the solution, and a Ni / SiNWs photoelectrocatalyst was prepared by photoelectrodeposition. The light intensity during the photoelectrodeposition was 100 mW·cm -2 , the deposition voltage is -1.5V, and the deposition time is 15 to 60s; (2) The Ni / SiNWs catalyst and sulfur powder were placed in two areas of a vacuum tube furnace, and then heated to different temperatures. A certain flow of N2 was introduced into the tube furnace to prepare the Ni3S2 / SiNWs cathode material for efficient hydrogen evolution from seawater photoelectrocatalysis. The vacuum degree in the tube furnace was 0.1-0.01 mBar, sulfur powder was placed in the inlet area of ​​the tube furnace, and the Ni / SiNWs catalyst was placed in the middle area of ​​the tube furnace. The Ni / SiNWs catalyst was placed vertically along the flow direction of nitrogen. When the temperature of the middle area reached 270°C, nitrogen began to flow in the tube. The nitrogen flow rate in the tube was 200 sccm. The inlet area was maintained at 125°C for 30 minutes, and the middle area was maintained at 300°C for 40 minutes.

2. The method for preparing a Ni3S2 / SiNWs cathode material for efficient photoelectrocatalytic hydrogen evolution in seawater according to claim 1, characterized in that: In step (1), the method for preparing the silicon nanowire substrate comprises the following steps: (101) The silicon wafer was ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 15–20 min in sequence. The cleaned silicon wafer was then placed in a mixed solution of sulfuric acid and hydrogen peroxide and kept at a constant temperature of 80 °C in a water bath for about 30–40 min to completely remove organic matter on its surface. (102) preparing an etching solution of a certain concentration consisting of nitric acid, ammonium fluoride, and silver nitrate, and a low-concentration and high-concentration silver removal solution consisting of nitric acid, hydrochloric acid, and deionized water; (103) The silicon wafer is sequentially placed into the three solutions prepared in step (102) to react and obtain a silicon nanowire substrate.

3. The method for preparing a Ni3S2 / SiNWs cathode material for efficient photoelectrocatalytic hydrogen evolution in seawater according to claim 2, characterized in that: In the step (101), the silicon wafer is a p-type silicon wafer with single-side polishing, a resistivity of 1-10Ω·cm, a length and a width of 1 cm, a thickness of 500 μm, and a volume ratio of sulfuric acid to hydrogen peroxide of 3:

1.

4. The method for preparing a Ni3S2 / SiNWs cathode material for efficient photoelectrocatalytic hydrogen evolution in seawater according to claim 2, characterized in that: In the step (102), the etching solution concentration composition is 1.85 mol / L nitric acid, 2.0 mol / L ammonium fluoride, and 0.02 mol / L silver nitrate. The volume ratio of nitric acid, hydrochloric acid, and deionized water in the low-concentration desilvering solution is 1:1:3, and the volume ratio of nitric acid, hydrochloric acid, and deionized water in the high-concentration desilvering solution is 1:1:

1.

5. The method for preparing a Ni3S2 / SiNWs cathode material for efficient photoelectrocatalytic hydrogen evolution in seawater according to claim 2, characterized in that: In the step (103), the etching temperature is 26° C., the etching time is 30 min, and the substrate is immersed in a low-concentration silver removal solution for 10 to 15 min, and then immersed in a high-concentration silver removal solution for 10 to 12 h.

6. The method for preparing a Ni3S2 / SiNWs cathode material for efficient photoelectrocatalytic hydrogen evolution in seawater according to claim 1, characterized in that: In the step (1), the concentration of the NiCl2 aqueous solution is 10.0 mmol / L, and the three-electrode system used is a Pt electrode as a counter electrode and an Ag / AgCl electrode as a reference electrode.

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