P-doped nickel layered double hydroxide cocatalyst heterojunction photocathode, preparation and application thereof

Abstract

The present application belongs to the technical field of photoelectrochemical hydrogen production, and discloses a P-doped nickel layered double hydroxide cocatalyst heterojunction photoanode and a preparation and application thereof. The P-doped nickel layered double hydroxide cocatalyst heterojunction photoanode comprises a Si substrate, an InN nanocolumn layer arranged on the Si substrate, a PM6 layer arranged on the surface of the InN nanocolumn, and a P-doped Ni LDH cocatalyst layer arranged on the surface of the PM6 layer. The present application further discloses a preparation method of the photoanode. In the photoanode, the P-doped Ni LDH cocatalyst not only increases the catalytic active sites of the reaction and reduces the activation energy required for HER, but also effectively reduces the onset potential of the heterojunction photoanode, promotes the dissociation, transport and reduction reaction of the photo-generated carriers at the electrode / electrolyte interface. The photoanode is used for photoelectrochemical water splitting to produce hydrogen, and solves the problems of high onset potential and low photoelectric conversion efficiency in the hydrogen production process.

Description

Technical Field

[0001] This invention belongs to the technical field of photoelectrochemical hydrogen production, specifically relating to a P-doped Ni LDH cocatalyst heterojunction photocathode, its preparation method, and its application. Background Technology

[0002] Developing photoelectrochemical (PEC) hydrogen production technology to convert solar energy into clean and renewable hydrogen energy is a promising approach that holds the potential to address the dual challenges of energy shortages and environmental pollution. InN nanopillars possess not only a wide light absorption range and high carrier mobility but also abundant catalytic reaction active sites, making them ideal photoelectrode materials for efficient hydrogen production. However, the large number of surface states and slow oxidation reaction kinetics of InN nanopillars often limit their PEC performance. Therefore, developing co-catalysts can not only improve the separation efficiency of photogenerated charges but also further reduce the overpotential required for water splitting, thereby enhancing the system's photoelectric conversion efficiency.

[0003] Existing literature discloses a method for preparing Ni-P nanocomposites using chemical vapor deposition, impregnation-reduction, and chemical reduction, and its application in PEC water splitting (Yaxin Li, Xin Yu, Juan Gao, et al. Hierarchical Ni2P / Zn-Ni-P nanosheet array for efficient energy-saving hydrogen evolution and hydrazine oxidation[J]. J Mater. Chem. A, 2023, 11, 2191-2202.). The Ni-P nanocomposites prepared in this work show particularly outstanding performance in hydrogen production, exhibiting excellent HER catalytic performance and promising application prospects. However, due to its relatively complex preparation process and relatively high cost, it is not conducive to large-scale production. Although it has shown good stability and catalytic performance in short-term experiments, its long-term stability still needs further verification to ensure its reliability and durability in practical applications.

[0004] Another literature discloses a method for preparing Ni-P nanocomposites using a solvent-assisted phase inversion, which demonstrates excellent performance in electrocatalytic water splitting and charge storage capacity (Anjali Gupta, Cassia A. Allison, Anuj Kumar, et al. Solvent-assisted phase modification of Ni-P material to boost electrocatalytic water splitting and charge storage capacity[J]. J EnergyStorage, 2024, 75, 109598.). This Ni-P nanocomposite achieved a maximum current density of 10 mA cm⁻¹ at a low overpotential of 1.23 V vs. RHE. -2 This indicates that it possesses excellent HER catalytic performance. Furthermore, the Ni-P nanocomposite material also demonstrates remarkable performance in charge storage capacity, showing excellent results at 3.0V vs. Li. + / Li exhibits excellent cycling stability and high specific capacity within the voltage window. Although the solvent-assisted phase inversion method for preparing Ni-P nanocomposites is relatively simple, its preparation process is still more complex compared to other electrocatalytic materials, hindering large-scale production. Furthermore, the flammability, explosiveness, and toxic gas release of the raw material NaBH4 necessitate extremely careful and cautious use and handling. In practical applications, safer and more environmentally friendly alternatives should be selected whenever possible.

[0005] This invention uses a P-doped Ni LDH cocatalyst, which not only increases the catalytic active sites of the reaction and reduces the activation energy required for HER, but also effectively reduces the onset potential of the heterojunction photoelectrode as a cocatalyst, promoting the dissociation, transport, and reduction reaction of photogenerated carriers at the electrode / electrolyte interface, thus providing an effective strategy for achieving efficient catalytic hydrogen production. Summary of the Invention

[0006] To overcome the shortcomings and deficiencies of existing technologies, the present invention aims to provide a p-doped nickel layered double hydroxide cocatalyst heterojunction photocathode and its preparation and application. By introducing a p-doped Ni LDH cocatalyst, the present invention significantly increases the number of catalytically active centers in the reaction, reduces the activation energy requirement for HER, optimizes the onset potential of the heterojunction photoelectrode, accelerates the separation and transport of photoinduced charge carriers, and effectively promotes their reduction reaction at the electrode / electrolyte interface. The p-doped Ni LDH cocatalyst heterojunction photocathode proposed in this invention, when used in a PEC system, not only possesses the characteristics of low cost, high catalytic activity, and continuous stability, but also solves the problems of high onset potential and low photoelectric conversion efficiency in the hydrogen production process. The p-doped nickel layered double hydroxide cocatalyst heterojunction photocathode of this invention is used for photoelectrochemical water splitting to produce hydrogen.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A P-doped nickel layered double hydroxide cocatalyst heterojunction photocathode includes a Si substrate, an InN nanopillar layer disposed on the Si substrate, a PM6 layer disposed on the surface of the InN nanopillars, and a P-doped Ni LDH cocatalyst disposed on the surface of the PM6 layer, wherein the P-doped Ni LDH layer is a two-dimensional nanosheet.

[0009] The P-doped Ni LDH cocatalyst is a P-doped nickel layered double hydroxide cocatalyst, specifically prepared by the following method: two-dimensional P-doped Ni LDH (i.e., P-doped nickel layered double hydroxide) nanosheets are deposited on a PM6 layer by electrochemical deposition, followed by drying to obtain the P-doped nickel layered double hydroxide cocatalyst. The electrochemical deposition includes chronoamperometry and galvanoamperometry.

[0010] During electrochemical deposition, the electrolyte is a mixture of a P source and a NiSO4 solution, with the concentration of the NiSO4 solution being 0.1–0.2 mol / L. The P source is NaH2PO2, and the doping amount of the P source is 1–20% of the molar amount of NiSO4, preferably 5–15%, and more preferably 8–12%.

[0011] The conditions for the constant current method are: current density of 8–12 mA / cm². 2 The deposition time is 30–120 seconds.

[0012] The conditions for the chronoamperometry method are a potential of 0.5–1.5V, preferably 1V, and a deposition time of 30–120s.

[0013] The structure of PM6 is

[0014] The Si substrate is n-type silicon with a conductivity of <0.005Ω; the InN nanopillars have a height of 100–400 nm, a diameter of 30–100 nm, and a density of 100–300 μm. -2 .

[0015] The preparation method of the P-doped Ni LDH cocatalyst heterojunction photocathode includes the following steps:

[0016] (1) InN nanopillars were grown on a Si substrate using molecular beam epitaxy.

[0017] (2) A PM6 layer was prepared on InN nanopillars;

[0018] (3) Two-dimensional nanosheets P-doped Ni LDH (P-doped nickel layered double hydroxide) were deposited on PM6 by electrochemical deposition and then dried.

[0019] Preferably, the InN nanopillars are fabricated on a Si substrate under the following process conditions:

[0020] Molecular beam epitaxy was employed, with the substrate temperature controlled at 350–450℃, the rotation speed at 5–10 r / min, and the In beam equivalent pressure at 1.0 × 10⁻⁶. -8 ~6×10 -7 Torr, nitrogen flow rate of 1-5 sccm, plasma source power of 300-500 W, growth time of 1-3 h.

[0021] The PM6 layer described in step (2) is prepared by drop coating.

[0022] The photocathode is used in a photoelectrochemical water splitting hydrogen production system.

[0023] The system includes a photoanode, a photocathode, an electrolyte, a light source, and an electrolytic cell; the photoanode and photocathode are respectively placed in the electrolyte, which is placed in the electrolytic cell; under sunlight irradiation, the photocathode produces hydrogen.

[0024] The photocathode is connected to a power source via wires. These wires are connected to the back side of the substrate in the photocathode via a Ti-Au alloy (Ti dissolves into the Si on the back side during thermal annealing to form a better ohmic contact, thus reducing resistance). The photocathode is immersed in an electrolyte. The wires are connected to the back side of the substrate and reinforced with Ag paste, then encapsulated with UV-curable adhesive.

[0025] The application of the photoelectrode in a photoelectrochemical water splitting hydrogen production system includes a photoanode, a photocathode, an electrolyte, a light source, and an electrolytic cell; the photoanode and photocathode are respectively placed in the electrolyte, and hydrogen is produced by the photoelectrode under sunlight irradiation.

[0026] The photoanode is Pt.

[0027] Preferably, the pH of the electrolyte is 12.5 to 13.5, and more preferably 13.

[0028] The electrolyte is a potassium hydroxide and sodium hydroxide solution; the sunlight irradiation method is parallel light irradiation.

[0029] The structural characteristics of phosphorus-doped Ni LDH (phosphorus-doped nickel layered double hydroxide) lie in the fact that the incorporation of phosphorus alters the electronic properties of Ni LDH, increases catalytic active sites, lowers the activation energy required for HER (hydrogen ion exchange), and improves catalytic efficiency. Furthermore, the introduction of phosphorus can effectively reduce the onset potential of the heterojunction photoelectrode, promote the separation and transport of photogenerated carriers, and improve photoelectric conversion efficiency. Moreover, phosphorus-doped Ni LDH exhibits good stability and durability, contributing to the realization of low-cost, highly efficient, and consistently stable PEC (photoelectric conversion) systems. In addition, this material also possesses a low onset potential, which helps to increase the rate and yield of hydrogen production, demonstrating high application potential.

[0030] The P-doped Ni LDH cocatalyst of this invention reduces the activation energy required for the reaction to a certain extent, increases the number of catalytically active sites, and promotes the separation and transport of photogenerated carriers, thereby achieving efficient and stable hydrogen production. This invention enables in-situ growth of the P-doped Ni LDH cocatalyst on a membrane.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] (1) The present invention uses P-doped Ni LDH cocatalyst, which effectively increases the catalytic active sites, reduces the activation energy required for HER, and improves the catalytic efficiency compared with the prior art.

[0033] (2) The present invention uses P-doped Ni LDH cocatalyst, which can effectively reduce the onset potential of heterojunction photoelectrode. Compared with the prior art, it promotes the separation and transport of photogenerated carriers and improves photoelectric conversion efficiency.

[0034] (3) The use of P-doped Ni LDH cocatalyst in this invention helps to achieve a low-cost, high-efficiency catalytic activity and a continuously stable PEC system, which solves the problems of high cost and unstable efficiency in the prior art and has a higher application prospect. Attached Figure Description

[0035] Figure 1 The diagram shows the structure of the heterojunction photocathode of the P-doped Ni LDH cocatalyst in Examples 1-4: 1-Si substrate, 2-InN nanopillar layer, 3-PM6 layer, 4-P-doped Ni LDH layer (i.e., phosphorus-doped nickel layered double hydroxide).

[0036] Figure 2 The figures for Examples 1-4 show the current-voltage relationship in a photoelectrochemical hydrogen production system using a P-doped Ni LDH cocatalyst heterojunction photocathode under bias. InN / PM6 / Ni-P-5% corresponds to Example 1, InN / PM6 / Ni-P-10% corresponds to Example 2, InN / PM6 / Ni-P-15% corresponds to Example 3, and InN / PM6 / Ni-P-20% corresponds to Example 4.

[0037] Figure 3 The current-voltage relationship diagrams of a Ni LDH cocatalyst heterojunction photocathode in the photoelectrochemical hydrogen production system under bias voltage are shown in Comparative Examples 1-4; InN / PM6 / NiLDH-30 corresponds to Comparative Example 1, InN / PM6 / NiLDH-60 corresponds to Comparative Example 2, InN / PM6 / NiLDH-90 corresponds to Comparative Example 3, and InN / PM6 / NiLDH-120 corresponds to Comparative Example 4.

[0038] Figure 4 The graphs show the bias photoelectric conversion efficiency of a P-doped Ni LDH cocatalyst heterojunction photocathode in the photoelectrochemical hydrogen production system under bias voltage in Examples 1-4; InN / PM6 / Ni-P-5% corresponds to Example 1, InN / PM6 / Ni-P-10% corresponds to Example 2, InN / PM6 / Ni-P-15% corresponds to Example 3, and InN / PM6 / Ni-P-20% corresponds to Example 4.

[0039] Figure 5 The graph shows the bias photoelectric conversion efficiency of a Ni LDH cocatalyst heterojunction photocathode in the photoelectrochemical hydrogen production system under bias voltage in Comparative Examples 1-4; InN / PM6 / NiLDH-30 corresponds to Comparative Example 1, InN / PM6 / NiLDH-60 corresponds to Comparative Example 2, InN / PM6 / NiLDH-90 corresponds to Comparative Example 3, and InN / PM6 / NiLDH-120 corresponds to Comparative Example 4. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.

[0041] A schematic diagram of a P-doped nickel layered double hydroxide cocatalyst heterojunction photocathode is shown below. Figure 1 As shown, it includes a Si substrate, an InN nanopillar layer disposed on the Si substrate, a PM6 layer disposed on the surface of the InN nanopillars, and a P-doped Ni LDH cocatalyst (i.e., phosphorus-doped nickel layered double hydroxide) disposed on the surface of the PM6 layer, wherein the P-doped Ni LDH layer is a two-dimensional nanosheet.

[0042] The back side of the Si substrate is connected to the wire via a Ti-Au alloy. The InN nanopillar layer on the Si substrate refers to the InN nanopillar layer on the front side of the Si substrate.

[0043] Example 1

[0044] The preparation of a P-doped Ni LDH cocatalyst heterojunction photocathode and its application in a bias-driven photoelectrochemical hydrogen production system includes the following steps:

[0045] (1) Substrate selection: n-type Si was used as the substrate (conductivity <0.005Ω).

[0046] (2) Photocathode fabrication: Molecular beam epitaxy was used, with the substrate temperature controlled at 400℃, the rotation speed at 10 r / min, and the In beam equivalent pressure at 6 × 10⁻⁶. -7 The growth process involved a nitrogen flow rate of 2.0 sccm, a plasma source power of 400 W, and a growth time of 2 h. The InN nanopillars had a height of 100–400 nm, a diameter of 30–100 nm, and a density of 100–300 μm³. -2 Then, a PM6 layer was prepared on InN nanopillars by drop-coating (PM6 was prepared into a solution using chlorobenzene, and then drop-coated at a concentration of 10 μL and a concentration of 10 mg / mL). Subsequently, two-dimensional P-doped Ni LDH nanosheets were deposited on the InN / PM6 heterojunction using electrochemical deposition and a constant current method, followed by annealing and drying (60 °C). The deposition conditions were as follows: NiSO4 solution concentration of 0.15 mol / L, P source of NaH2PO2 at 5% of the molar amount of NiSO4, and current density of 10 mA / cm². 2 The deposition time was 60s to obtain the photocathode; finally, the wires were connected to the back side of the Si substrate of the photocathode using a Ti-Au alloy.

[0047] (3) Construction of photoelectrochemical cell: The prepared photocathode was connected in series with the Pt electrode through a wire, the light source was parallel light, and the electrolyte was 0.1M KOH electrolyte (pH=13).

[0048] like Figure 2 and 4 As shown, in this embodiment, a P-doped Ni LDH cocatalyst heterojunction photocathode is used in a photoelectrochemical hydrogen production system under a certain bias voltage for solar hydrogen production. The bias voltage photoelectric conversion efficiency obtained at -0.5V vs. RHE is 18.95%.

[0049] Example 2

[0050] The preparation of a P-doped Ni LDH cocatalyst heterojunction photocathode and its application in a bias-driven photoelectrochemical hydrogen production system includes the following steps:

[0051] (1) Substrate selection: n-type Si was used as the substrate (conductivity <0.005Ω).

[0052] (2) Photocathode fabrication: Molecular beam epitaxy was used, with the substrate temperature controlled at 400℃, the rotation speed at 10 r / min, and the In beam equivalent pressure at 6 × 10⁻⁶. -7 The growth process involved a nitrogen flow rate of 2.0 sccm, a plasma source power of 400 W, and a growth time of 2 h. The InN nanopillars had a height of 100–400 nm, a diameter of 30–100 nm, and a density of 100–300 μm³. -2 Then, a PM6 layer was prepared on InN nanopillars using a drop-coating method (the PM6 layer and InN form a heterojunction, enhancing the absorption of the heterojunction in the visible light region); subsequently, two-dimensional P-doped Ni LDH nanosheets were deposited on the InN / PM6 heterojunction using electrochemical deposition and a constant current method, followed by annealing and drying on a hot stage; the deposition conditions were as follows: NiSO4 solution concentration was 0.15 mol / L, P source was NaH2PO2 with a doping amount of 10% of the molar amount of NiSO4, and current density was 10 mA / cm². 2 The deposition time was 60s to obtain the photocathode; finally, the wires were connected to the back side of the Si substrate of the photocathode using a Ti-Au alloy.

[0053] (3) Construction of photoelectrochemical cell: The prepared photocathode was connected in series with the Pt electrode through a wire, the light source was parallel light, and the electrolyte was 0.1M KOH electrolyte (pH=13).

[0054] like Figure 2 and 4 As shown, in this embodiment, a P-doped Ni LDH cocatalyst heterojunction photocathode is used in a photoelectrochemical hydrogen production system under a certain bias voltage for solar hydrogen production. The bias voltage photoelectric conversion efficiency obtained at -0.5V vs. RHE is 19.80%.

[0055] Example 3

[0056] The preparation of a P-doped Ni LDH cocatalyst heterojunction photocathode and its application in a bias-driven photoelectrochemical hydrogen production system includes the following steps:

[0057] (1) Substrate selection: n-type Si was used as the substrate (conductivity <0.005Ω).

[0058] (2) Photocathode fabrication: Molecular beam epitaxy was used, with the substrate temperature controlled at 400℃, the rotation speed at 10 r / min, and the In beam equivalent pressure at 6 × 10⁻⁶. -7 The growth process involved a nitrogen flow rate of 2.0 sccm, a plasma source power of 400 W, and a growth time of 2 h. The InN nanopillars had a height of 100–400 nm, a diameter of 30–100 nm, and a density of 100–300 μm³. -2 Then, a PM6 layer was prepared on InN nanopillars using a drop-coating method; subsequently, two-dimensional P-doped Ni LDH nanosheets were deposited on the InN / PM6 heterojunction using electrochemical deposition and a constant current method, followed by annealing and drying; the deposition conditions were as follows: NiSO4 solution concentration was 0.15 mol / L, P source was NaH2PO2 with a doping content of 15% of NiSO4 molar, and current density was 10 mA / cm². 2 The deposition time was 60s to obtain the photocathode; finally, the wires were connected to the back side of the Si substrate of the photocathode using a Ti-Au alloy.

[0059] (3) Construction of photoelectrochemical cell: The prepared photocathode was connected in series with the Pt electrode through a wire, the light source was parallel light, and the electrolyte was 0.1M KOH electrolyte (pH=13).

[0060] like Figure 2 and 4 As shown, in this embodiment, a P-doped Ni LDH cocatalyst heterojunction photocathode is used in a photoelectrochemical hydrogen production system under a certain bias voltage for solar hydrogen production. The bias voltage photoelectric conversion efficiency obtained at -0.5V vs. RHE is 17.34%.

[0061] Example 4

[0062] The preparation of a P-doped Ni LDH cocatalyst heterojunction photocathode and its application in a bias-driven photoelectrochemical hydrogen production system includes the following steps:

[0063] (1) Substrate selection: n-type Si was used as the substrate (conductivity <0.005Ω).

[0064] (2) Photocathode fabrication: Molecular beam epitaxy was used, with the substrate temperature controlled at 400℃, the rotation speed at 10 r / min, and the In beam equivalent pressure at 6 × 10⁻⁶. -7 The growth process involved a nitrogen flow rate of 2.0 sccm, a plasma source power of 400 W, and a growth time of 2 h. The InN nanopillars had a height of 100–400 nm, a diameter of 30–100 nm, and a density of 100–300 μm³. -2Then, a PM6 layer was prepared on InN nanopillars using a drop-coating method; subsequently, two-dimensional P-doped Ni LDH nanosheets were deposited on the InN / PM6 heterojunction using electrochemical deposition and a constant current method, followed by annealing and drying; the deposition conditions were as follows: NiSO4 solution concentration was 0.15 mol / L, P source was NaH2PO2 with a doping amount of 20% of the molar amount of NiSO4, and current density was 10 mA / cm². 2 The deposition time was 60s to obtain the photocathode; finally, the wires were connected to the back side of the Si substrate of the photocathode using a Ti-Au alloy.

[0065] (3) Construction of photoelectrochemical cell: The prepared photocathode was connected in series with the Pt electrode through a wire, the light source was parallel light, and the electrolyte was 0.1M KOH electrolyte (pH=13).

[0066] like Figure 2 and 4 As shown, in this embodiment, a P-doped Ni LDH cocatalyst heterojunction photocathode is used in a photoelectrochemical hydrogen production system under a certain bias voltage for solar hydrogen production. The bias voltage photoelectric conversion efficiency obtained at -0.5V vs. RHE is 9.89%.

[0067] Comparative Example 1

[0068] The preparation of a Ni LDH cocatalyst heterojunction photocathode and its application in a bias-voltage photoelectrochemical hydrogen production system includes the following steps:

[0069] (1) Substrate selection: n-type Si was used as the substrate (conductivity <0.005Ω).

[0070] (2) Photocathode fabrication: Molecular beam epitaxy was used, with the substrate temperature controlled at 400℃, the rotation speed at 10 r / min, and the In beam equivalent pressure at 6 × 10⁻⁶. -7 The growth process involved a nitrogen flow rate of 2.0 sccm, a plasma source power of 400 W, and a growth time of 2 h. The InN nanopillars had a height of 100–400 nm, a diameter of 30–100 nm, and a density of 100–300 μm³. -2 Then, a PM6 layer was prepared on InN nanopillars using a drop-coating method; subsequently, two-dimensional Ni LDH nanosheets were deposited on the InN / PM6 heterojunction using electrochemical deposition and a constant current method, followed by annealing and drying; the deposition conditions were: NiSO4 solution concentration of 0.15 mol / L and current density of 10 mA / cm². 2 The deposition time was 30s to obtain the photocathode; finally, the wires were connected to the back side of the Si substrate of the photocathode using a Ti-Au alloy.

[0071] (3) Construction of photoelectrochemical cell: The prepared photocathode was connected in series with the Pt electrode through a wire, the light source was parallel light, and the electrolyte was 0.1M KOH electrolyte (pH=13).

[0072] like Figure 3 and 5 As shown, a Ni LDH cocatalyst heterojunction photocathode in this comparative example is used for solar hydrogen production in a photoelectrochemical hydrogen production system under a certain bias voltage. The bias voltage photoelectric conversion efficiency obtained at -0.5V vs. RHE is 5.39%.

[0073] Comparative Example 2

[0074] The preparation of a Ni LDH cocatalyst heterojunction photocathode and its application in a bias-voltage photoelectrochemical hydrogen production system includes the following steps:

[0075] (1) Substrate selection: n-type Si was used as the substrate (conductivity <0.005Ω).

[0076] (2) Photocathode fabrication: Molecular beam epitaxy was used, with the substrate temperature controlled at 400℃, the rotation speed at 10 r / min, and the In beam equivalent pressure at 6 × 10⁻⁶. -7 The growth process involved a nitrogen flow rate of 2.0 sccm, a plasma source power of 400 W, and a growth time of 2 h. The InN nanopillars had a height of 100–400 nm, a diameter of 30–100 nm, and a density of 100–300 μm³. -2 Then, a PM6 layer was prepared on InN nanopillars using a drop-coating method; subsequently, two-dimensional Ni LDH nanosheets were deposited on the InN / PM6 heterojunction using electrochemical deposition and a constant current method, followed by annealing and drying; the deposition conditions were: NiSO4 solution concentration of 0.15 mol / L and current density of 10 mA / cm². 2 The deposition time was 60s to obtain the photocathode; finally, the wires were connected to the back side of the Si substrate of the photocathode using a Ti-Au alloy.

[0077] (3) Construction of photoelectrochemical cell: The prepared photocathode was connected in series with the Pt electrode through a wire, the light source was parallel light, and the electrolyte was 0.1M KOH electrolyte (pH=13).

[0078] like Figure 3 and 5 As shown, a Ni LDH cocatalyst heterojunction photocathode in this comparative example is used for solar hydrogen production in a photoelectrochemical hydrogen production system under a certain bias voltage. The bias voltage photoelectric conversion efficiency obtained at -0.5V vs. RHE is 16.86%.

[0079] Comparative Example 3

[0080] The preparation of a Ni LDH cocatalyst heterojunction photocathode and its application in a bias-voltage photoelectrochemical hydrogen production system includes the following steps:

[0081] (1) Substrate selection: n-type Si was used as the substrate (conductivity <0.005Ω).

[0082] (2) Photocathode fabrication: Molecular beam epitaxy was used, with the substrate temperature controlled at 400℃, the rotation speed at 10 r / min, and the In beam equivalent pressure at 6 × 10⁻⁶. -7 The growth process involved a nitrogen flow rate of 2.0 sccm, a plasma source power of 400 W, and a growth time of 2 h. The InN nanopillars had a height of 100–400 nm, a diameter of 30–100 nm, and a density of 100–300 μm³. -2 Then, a PM6 layer was prepared on InN nanopillars using a drop-coating method; subsequently, two-dimensional Ni LDH nanosheets were deposited on the InN / PM6 heterojunction using electrochemical deposition and a constant current method, followed by annealing and drying; the deposition conditions were: NiSO4 solution concentration of 0.15 mol / L and current density of 10 mA / cm². 2 The deposition time was 90s to obtain the photocathode; finally, the wires were connected to the back side of the Si substrate of the photocathode using a Ti-Au alloy.

[0083] (3) Construction of photoelectrochemical cell: The prepared photocathode was connected in series with the Pt electrode through a wire, the light source was parallel light, and the electrolyte was 0.1M KOH electrolyte (pH=13).

[0084] like Figure 3 and 5 As shown, a Ni LDH cocatalyst heterojunction photocathode in this comparative example is used for solar hydrogen production in a photoelectrochemical hydrogen production system under a certain bias voltage. The bias voltage photoelectric conversion efficiency obtained at -0.5V vs. RHE is 9.17%.

[0085] Comparative Example 4

[0086] The preparation of a Ni LDH cocatalyst heterojunction photocathode and its application in a bias-voltage photoelectrochemical hydrogen production system includes the following steps:

[0087] (1) Substrate selection: n-type Si was used as the substrate (conductivity <0.005Ω).

[0088] (2) Photocathode fabrication: Molecular beam epitaxy was used, with the substrate temperature controlled at 400℃, the rotation speed at 10 r / min, and the In beam equivalent pressure at 6 × 10⁻⁶. -7The growth process involved a nitrogen flow rate of 2.0 sccm, a plasma source power of 400 W, and a growth time of 2 h. The InN nanopillars had a height of 100–400 nm, a diameter of 30–100 nm, and a density of 100–300 μm³. -2 Then, a PM6 layer was prepared on InN nanopillars using a drop-coating method; subsequently, two-dimensional Ni LDH nanosheets were deposited on the InN / PM6 heterojunction using electrochemical deposition and a constant current method, followed by annealing and drying; the deposition conditions were: NiSO4 solution concentration of 0.15 mol / L and current density of 10 mA / cm². 2 The deposition time was 120s to obtain the photocathode; finally, the wires were connected to the back side of the Si substrate of the photocathode using a Ti-Au alloy.

[0089] (3) Construction of photoelectrochemical cell: The prepared photocathode was connected in series with the Pt electrode through a wire, the light source was parallel light, and the electrolyte was 0.1M KOH electrolyte (pH=13).

[0090] like Figure 3 and 5 As shown, a Ni LDH cocatalyst heterojunction photocathode in this comparative example is used for solar hydrogen production in a photoelectrochemical hydrogen production system under bias voltage. The bias voltage photoelectric conversion efficiency obtained at -0.5V vs. RHE is 10.48%.

[0091] Figure 2 The figures for Examples 1-4 show the current-voltage relationship in a photoelectrochemical hydrogen production system using a P-doped Ni LDH cocatalyst heterojunction photocathode under bias. InN / PM6 / Ni-P-5% corresponds to Example 1, InN / PM6 / Ni-P-10% corresponds to Example 2, InN / PM6 / Ni-P-15% corresponds to Example 3, and InN / PM6 / Ni-P-20% corresponds to Example 4.

[0092] Figure 3 The current-voltage relationship diagrams of a Ni LDH cocatalyst heterojunction photocathode in the photoelectrochemical hydrogen production system under bias voltage are shown in Comparative Examples 1-4; InN / PM6 / NiLDH-30 corresponds to Comparative Example 1, InN / PM6 / NiLDH-60 corresponds to Comparative Example 2, InN / PM6 / NiLDH-90 corresponds to Comparative Example 3, and InN / PM6 / NiLDH-120 corresponds to Comparative Example 4.

[0093] Figure 4The graphs show the bias photoelectric conversion efficiency of a P-doped Ni LDH cocatalyst heterojunction photocathode in the photoelectrochemical hydrogen production system under bias voltage in Examples 1-4; InN / PM6 / Ni-P-5% corresponds to Example 1, InN / PM6 / Ni-P-10% corresponds to Example 2, InN / PM6 / Ni-P-15% corresponds to Example 3, and InN / PM6 / Ni-P-20% corresponds to Example 4.

[0094] Figure 5 The graph shows the bias photoelectric conversion efficiency of a Ni LDH cocatalyst heterojunction photocathode in the photoelectrochemical hydrogen production system under bias voltage in Comparative Examples 1-4; InN / PM6 / NiLDH-30 corresponds to Comparative Example 1, InN / PM6 / NiLDH-60 corresponds to Comparative Example 2, InN / PM6 / NiLDH-90 corresponds to Comparative Example 3, and InN / PM6 / NiLDH-120 corresponds to Comparative Example 4.

[0095] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A P-doped nickel layered double hydroxide cocatalyst heterojunction photocathode, characterized in that: The substrate includes a Si substrate, an InN nanopillar layer disposed on the Si substrate, a PM6 layer disposed on the surface of the InN nanopillar layer, and a P-doped NiLDH cocatalyst layer disposed on the surface of the PM6 layer, wherein the P-doped NiLDH cocatalyst layer is a two-dimensional nanosheet. The P-doped Ni LDH cocatalyst is a P-doped nickel layered double hydroxide cocatalyst, which is prepared by the following method: two-dimensional nanosheets of P-doped Ni LDH are deposited on a PM6 layer by electrochemical deposition, and then dried to obtain the P-doped nickel layered double hydroxide cocatalyst; the electrochemical deposition includes chronoamperometry and galvanoamperometry. During electrochemical deposition, the electrolyte solution is a mixture of P source and NiSO4 solution, with the concentration of NiSO4 solution being 0.1~0.2 mol / L, the P source being NaH2PO2, and the doping amount of the P source being 1~20% of the molar amount of NiSO4.

2. The P-doped nickel layered double hydroxide co-catalyst heterojunction photocathode according to claim 1, characterized in that: The doping amount of the P source is 5-15% of the molar amount of NiSO4; The conditions for the constant current method are: current density of 8~12 mA / cm². 2 The deposition time is 30~120 s; Conditions for chronoamperometry: potential 0.5~1.5V, deposition time 30~120 s.

3. The P-doped nickel layered double hydroxide co-catalyst heterojunction photocathode according to claim 2, characterized in that: The doping amount of the P source is 8-12% of the molar amount of NiSO4.

4. The P-doped nickel layered double hydroxide co-catalyst heterojunction photocathode according to claim 1, characterized in that: The Si substrate is n-type silicon with a conductivity <0.005 Ω; the InN nanopillars have a height of 100~400 nm, a diameter of 30~100 nm, and a density of 100~300 mm². -2 .

5. The method for preparing the P-doped nickel layered double hydroxide co-catalyst heterojunction photocathode according to any one of claims 1 to 4, characterized in that: Includes the following steps: (1) InN nanopillars were grown on a Si substrate using molecular beam epitaxy. (2) A PM6 layer was prepared on InN nanopillars; (3) Two-dimensional nanosheets of P-doped Ni LDH cocatalyst were deposited on PM6 by electrochemical deposition and then dried.

6. The method for preparing the P-doped nickel layered double hydroxide co-catalyst heterojunction photocathode according to claim 5, characterized in that: The conditions for the molecular beam epitaxy process described in step (1) are as follows: substrate temperature is controlled at 350~450℃, rotation speed is 5~10 r / min, and In beam equivalent pressure is 1.0×10⁻⁶. -8 ~6×10 -7 Torr, nitrogen flow rate of 1~5 sccm, plasma source power of 300~500 W, growth time of 1~3 h; The electrochemical deposition described in step (3) includes chronoamperometry and galvanoamperometry; During electrochemical deposition, the electrolyte solution is a mixture of a P source and a NiSO4 solution, with the NiSO4 solution concentration being 0.1~0.2 mol / L. The P source is NaH2PO2, and the doping amount of the P source is 1~20% of the molar amount of NiSO4. The conditions for the constant current method are: current density of 8~12 mA / cm². 2 The deposition time is 30~120 s; The conditions for the chronoamperometry method are a potential of 0.5~1.5V and a deposition time of 30~120 s; The PM6 layer described in step (2) is prepared by drop coating.

7. The application of the P-doped nickel layered double hydroxide co-catalyst heterojunction photocathode according to any one of claims 1 to 4, characterized in that: The P-doped nickel layered double hydroxide cocatalyst heterojunction photocathode is used in a photoelectrochemical water splitting hydrogen production system.

8. The application according to claim 7, characterized in that: The system includes a photoanode, a photocathode, an electrolyte, a light source, and an electrolytic cell; the photoanode and photocathode are respectively placed in the electrolyte, and the electrolyte is placed in the electrolytic cell; Hydrogen is produced by a photocathode under sunlight.

9. The application according to claim 8, characterized in that: The back side of the Si substrate in the photocathode is connected to the wire via a Ti-Au alloy; the photoanode and photocathode are connected in series via wires. The photoanode is Pt; The pH of the electrolyte is 12.5~13.5; The electrolyte is a potassium hydroxide and sodium hydroxide solution; the sunlight irradiation method is parallel light irradiation.

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