A silicon nanowire substrate-based photocathode, a preparation method and application thereof

Abstract

The application discloses a kind of photoelectric cathode based on silicon nanowire substrate and its preparation method and application, belong to photoelectric catalytic reduction carbon dioxide material technical field.The preparation method disclosed in the application adsorbs Au nanoparticles on the surface of silicon nanowire substrate, obtains the silicon nanowire substrate with Au nanoparticles being adsorbed;TiO2 Film is deposited on the surface of silicon nanowire substrate by atomic layer deposition method, then photosensitizer and catalyst are adsorbed on the TiO2 Film by atomic layer deposition method, and TiO2 Film is coated by atomic layer deposition method, to obtain photoelectric cathode based on silicon nanowire substrate.The photoelectric cathode obtained by the method has the advantages of stable structure, good carbon dioxide reduction effect and the like, and has important significance for optimizing the structure of dye-sensitized photoelectric cathode and improving its photoelectric catalytic carbon dioxide reduction performance.

Description

Technical Field

[0001] This invention belongs to the field of photoelectrocatalytic reduction of carbon dioxide materials technology, specifically relating to a photocathode based on a silicon nanowire substrate, its preparation method, and its application. Background Technology

[0002] Dye-sensitized photoelectrochemical cells (DSPECs) for photoelectrocatalytic CO2 reduction have attracted significant attention in the field of energy materials due to their advantages such as low raw material cost, simple preparation process, and tunable surface assembly. In DSPECs, the CO2 reduction reaction occurs at the photocathode, which consists of a semiconductor substrate, a photosensitizer, and a catalyst. When the photosensitizer is excited by visible light, it transitions from its ground state to an excited state, generating photoelectron-hole pairs. Photogenerated holes are injected into the valence band of the semiconductor, while photogenerated electrons migrate to the catalyst surface, driving CO2 reduction and converting CO2 into valuable chemical substances such as CO.

[0003] However, using DSPEC for CO2 reduction has certain limitations. The catalysts in DSPEC (usually metal complexes or molecular catalysts) are prone to deactivation during prolonged photoelectrochemical reactions, especially in aqueous solutions or electrolytes, where their stability is poor and they are easily decomposed or degraded. The adsorption and desorption processes of the catalyst on the electrode surface are unstable, easily leading to catalyst loss and affecting the continuation of the reaction. Simultaneously, the photosensitizers in DSPEC (usually dye molecules) are prone to photodegradation under light conditions, especially under strong or prolonged light exposure. The photosensitizers are unstable, resulting in decreased photoelectric conversion efficiency. Furthermore, the unstable adsorption and desorption processes of the photosensitizer on the electrode surface easily lead to photosensitizer loss, further affecting photoelectric conversion efficiency. In addition, CO2 reduction reactions typically produce multiple reduction products (such as CO, HCOOH, CH4, C2H4, etc.), posing a challenge to controlling product selectivity in DSPEC systems, making it difficult to efficiently generate a single target product. Moreover, because CO2 reduction involves multiple electron transfer processes, the reaction kinetics are slow, resulting in low photoelectric conversion efficiency and CO2 reduction efficiency in DSPEC systems.

[0004] Because the CO2 reduction reaction using DSPEC has poor selectivity for CO2 reduction products and poor stability of photosensitizers and catalysts, improving the selectivity and stability of photocatalytic CO2 reduction products has become the key to improving photoelectrochemical CO2 reduction.

[0005] In summary, obtaining a photocathode with stable structure, good photoelectrocatalytic performance, simple preparation process, and high selectivity is of great significance for optimizing the structure of dye-sensitized photocathodes and improving the selective performance of carbon dioxide reduction. Summary of the Invention

[0006] The purpose of this invention is to provide a photocathode based on a silicon nanowire substrate, its preparation method, and its application, in order to improve and solve the technical problems of poor selectivity and poor stability of CO2 reduction products in existing photocathodes.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] This invention discloses a method for fabricating a photocathode based on a silicon nanowire substrate, comprising the following steps:

[0009] Au nanoparticles are adsorbed onto the surface of a silicon nanowire substrate to obtain a silicon nanowire substrate with adsorbed Au nanoparticles.

[0010] A TiO2 film was deposited on the surface of a silicon nanowire substrate by atomic layer deposition (ALD). Subsequently, a photosensitizer and a catalyst were adsorbed onto the TiO2 film deposited by ALD. The TiO2 film was then coated by ALD to obtain a photocathode based on a silicon nanowire substrate.

[0011] Furthermore, the method for preparing the silicon nanowire substrate is as follows:

[0012] After processing the silicon wafer, a silicon wafer is obtained. The silicon wafer is then immersed in AgNO3 solution for 60-90 min and HF solution for 60-90 min in sequence, and then immersed in HNO3 solution for 60-90 min and HF solution for 5-10 min in sequence to obtain a silicon nanowire substrate.

[0013] The steps for processing the silicon wafer are as follows:

[0014] The silicon wafer was then washed in a mixed solution of H2SO4 and H2O2 at a volume ratio of 1:1 for 20-40 minutes to obtain the wafer.

[0015] The concentrations of the AgNO3 solution and the HF solution were 0.03~0.05 M and 4.3~4.6 M, respectively.

[0016] Furthermore, the adsorption of Au nanoparticles onto the surface of the silicon nanowire substrate is achieved by immersing the silicon nanowire substrate in a HAuCl4 solution and oscillating it; the concentration of the HAuCl4 solution is 0.002~0.1 M.

[0017] Furthermore, the oscillation frequency is 120~150 rpm, and the duration is 60~90 min.

[0018] Furthermore, the specific steps for depositing a TiO2 thin film on the silicon nanowire substrate using atomic layer deposition are as follows:

[0019] A silicon nanowire substrate was placed in a deposition chamber, and a deposition reaction was carried out using tetra(dimethylamino)titanium and water as precursors to form a TiO2 film on the surface of the silicon nanowire substrate.

[0020] The deposition reaction temperature of the tetra(dimethylamino)titanium is 60~120 ℃.

[0021] Furthermore, the TiO2 film is deposited on the silicon nanowire substrate for 15 cycles.

[0022] Furthermore, the photosensitizer is a P1 photosensitizer; the catalyst is a ReC catalyst;

[0023] The steps for adsorbing photosensitizers and catalysts onto TiO2 thin films deposited by atomic layer deposition are as follows:

[0024] The substrate was placed in the atomic layer deposition reaction chamber to deposit a TiO2 film, and then immersed in an acetonitrile solution of P1 photosensitizer for further TiO2 film deposition; subsequently, it was immersed in a methanol solution of ReC catalyst for outermost TiO2 film coating.

[0025] The photosensitizer is deposited in 5 cycles; the catalyst is deposited in 5 cycles.

[0026] The concentration of the acetonitrile solution of the P1 photosensitizer is 0.2~0.3 mM; the concentration of the methanol solution of the ReC catalyst is 0.2~0.6 mM.

[0027] Furthermore, the specific steps for coating TiO2 thin films using atomic layer deposition are as follows:

[0028] TiO2 thin films were deposited using tetra(dimethylamino)titanium and water as precursors to obtain photocathodes based on silicon nanowire substrates;

[0029] The TiO2 thin film was deposited in 5 cycles.

[0030] The present invention also discloses a photocathode based on a silicon nanowire substrate prepared by the above preparation method.

[0031] This invention also discloses the application of the above-mentioned silicon nanowire-based photocathode in photoelectrocatalytic carbon dioxide reduction, including the following steps:

[0032] Using a silicon nanowire-based photocathode as the working electrode, Ag / Ag + A three-electrode system was constructed using a reference electrode and a platinum sheet as the counter electrode. Photoelectrocatalytic carbon dioxide reduction was carried out in the electrolyte solution of the three-electrode system.

[0033] The incident light power intensity of the light source used in the photoelectrocatalytic carbon dioxide reduction reaction is 100 mW / cm². 2 The applied bias voltage range is -1.3 to -1.9 V;

[0034] The electrolyte solution is an acetonitrile solution containing 0.1 M tetrabutylammonium hexafluorophosphate.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] This invention discloses a method for preparing a photocathode based on a silicon nanowire substrate. Atomic layer deposition (ALD) is used to connect a photosensitizer and a catalyst onto the silicon nanowire substrate, and Au particles are adsorbed onto the silicon nanowire substrate. This method achieves a stable photocathode without the need for covalent or ionic bonds between photosensitizer / catalyst units, resulting in a more stable structure and better photocatalytic performance. Utilizing the plasmon resonance effect of the metal nanostructure, the photo-matter interaction is significantly enhanced, promoting the catalytic reaction, increasing the utilization of visible light, and improving the selectivity of CO2 reduction. A simple atomic layer deposition coating of TiO2 is applied to the outermost layer of the photocathode to maintain the stability of the catalyst during the reaction, further enhancing the stability of the photocathode structure.

[0037] The present invention also discloses a photocathode based on a silicon nanowire substrate prepared by the above preparation method. This photocathode has the advantages of stable structure and good carbon dioxide reduction effect, which is of great significance for optimizing the structure of dye-sensitized photocathode and improving its photoelectrocatalytic water oxidation performance. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the photocathode based on a silicon nanowire substrate according to the present invention;

[0039] Figure 2 The image shows the ultraviolet-visible absorption spectrum of the photocathode based on a silicon nanowire substrate prepared in Example 1 of this invention.

[0040] Figure 3 This is a Faraday effect diagram of CO2 reduction products of a photocathode based on a silicon nanowire substrate obtained in Example 1 of the present invention.

[0041] Figure 4 This is a photocurrent-time curve of a photocathode based on a silicon nanowire substrate obtained in Example 1 of the present invention;

[0042] Figure 5 The Nyquist plot is of the photocathode based on a silicon nanowire substrate obtained in Example 1 of this invention. Detailed Implementation

[0043] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0044] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0045] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0046] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0047] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0048] This invention provides a method for fabricating a photocathode based on a silicon nanowire substrate, comprising the following steps:

[0049] Au nanoparticles are adsorbed onto the surface of a silicon nanowire substrate (Si NWs substrate) to obtain a silicon nanowire substrate (Si NWs|Au) with adsorbed Au nanoparticles.

[0050] A TiO2 thin film (Si NWs|Au|TiO2) was deposited on the surface of a silicon nanowire substrate by atomic layer deposition. Subsequently, photosensitizers and catalysts were deposited and adsorbed onto the TiO2 thin film by atomic layer deposition. The TiO2 thin film was then coated by atomic layer deposition to obtain a photocathode based on a silicon nanowire substrate (Si NWs|Au|TiO2|P1-TiO2|ReC-TiO2).

[0051] Preferably, the method for preparing silicon nanowire substrates by metal-assisted chemical etching is as follows:

[0052] After processing the silicon wafer, a silicon wafer is obtained. The silicon wafer is then immersed in AgNO3 solution and HF solution in sequence to obtain a silicon nanowire substrate.

[0053] The steps for processing the silicon wafer are as follows:

[0054] p-type silicon wafers were ultrasonically immersed in acetone, ethanol and water for 20-30, 15-30 and 15-30 min respectively, and then cleaned in a mixed solution of H2SO4 and H2O2 for 30-50 min to obtain silicon wafers.

[0055] The silicon wafer is immersed in AgNO3 solution and HF solution for 60-90 min;

[0056] The concentrations of the AgNO3 solution and the HF solution were 0.03~0.05 M and 4.3~4.6 M, respectively.

[0057] Preferably, the Au nanoparticles are adsorbed onto the surface of the silicon nanowire substrate by immersing the silicon nanowire substrate in a HAuCl4 solution and oscillating it in an oscillator; the oscillation frequency in the oscillator is 120 rpm and the time is 60 min.

[0058] Preferably, the specific steps for depositing a TiO2 thin film on the silicon nanowire substrate using atomic layer deposition are as follows:

[0059] A silicon nanowire substrate was placed in a deposition chamber, and a deposition reaction was carried out using tetra(dimethylamino)titanium and water as precursors to form a TiO2 film on the surface of the silicon nanowire substrate.

[0060] The deposition reaction temperature of the tetra(dimethylamino)titanium is 60~120 ℃.

[0061] Preferably, the TiO2 film is deposited on the silicon nanowire substrate for 15 cycles.

[0062] Preferably, the step of adsorbing the photosensitizer and catalyst onto the TiO2 thin film deposited by atomic layer deposition is as follows:

[0063] The substrate was placed in an atomic layer deposition reaction chamber to deposit a TiO2 film, and then immersed in an acetonitrile solution of P1 photosensitizer for photosensitizer adsorption; after drying, it was placed in an atomic layer deposition reaction chamber to deposit a TiO2 film, and then immersed in a methanol solution of ReC catalyst for catalyst adsorption.

[0064] The photosensitizer is deposited in 5 cycles; the catalyst is deposited in 5 cycles.

[0065] The concentration of the acetonitrile solution of the P1 photosensitizer is 0.2~0.3 mM; the concentration of the methanol solution of the ReC catalyst is 0.5~0.6 mM.

[0066] The specific steps for coating TiO2 thin films using atomic layer deposition are as follows:

[0067] TiO2 thin films were deposited using tetra(dimethylamino)titanium and water as precursors to obtain photocathodes based on silicon nanowire substrates;

[0068] The TiO2 thin film was deposited in 5 cycles.

[0069] The present invention also provides a photocathode based on a silicon nanowire substrate prepared by the above preparation method, with the structure Si NWs|Au|TiO2|4-(Bis-{4-[5-(2,2-dicyano-vinyl)-thiophene-2-yl]-phenyl}-amino)-benzoicacid(P1)-TiO2|[Re(bdpm-bpy)(CO)3Cl](ReC)-TiO2, abbreviated as Si NWs|Au|TiO2|P1-TiO2|ReC-TiO2.

[0070] This invention also provides the application of the above-mentioned silicon nanowire-based photocathode in carbon dioxide reduction, wherein the application process uses the prepared photocathode as the working electrode and Ag / Ag + A three-electrode system was constructed using a reference electrode and a platinum sheet as the counter electrode to carry out photoelectrocatalytic carbon dioxide reduction reaction in an electrolyte solution.

[0071] Preferably, the incident light power intensity of the light source used for photoelectrocatalysis is 100 mW / cm². 2 The applied bias voltage range is -1.3 to -1.9 V vs Ag / Ag + .

[0072] Preferably, the electrolyte solution is an acetonitrile solution containing 0.1 M tetrabutylammonium hexafluorophosphate.

[0073] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0074] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0075] Example 1

[0076] A method for fabricating a photocathode based on a silicon nanowire substrate includes the following steps:

[0077] Si NWs were prepared by metal-assisted chemical etching. First, p-type silicon wafers were ultrasonically immersed in acetone, ethanol, and water for 20, 15, and 15 min, respectively, to remove surface impurities. Then, they were further cleaned in H2SO4:H2O2 (v / v = 1:1) solution for 30 min, rinsed with water, and the surface oxide layer was removed in HF solution (5 wt%). The clean silicon wafers were then immersed in solutions containing AgNO3 (0.03 M) and 4.6 M HF for 90 min at room temperature. The silicon wafers were then immersed in HNO3 solution (v / v = 1:1) for 45 min to remove residual Ag. Finally, they were immersed in HF solution (5 wt%) for 5 min to obtain vertically aligned Si NWs.

[0078] Si NWs were immersed in HAuCl4 solution (2 mM) and shaken at a frequency of 120 rpm for 60 min. After rinsing with water, a silicon nanowire substrate (Si NWs|Au) with adsorbed Au nanoparticles was obtained.

[0079] Si NWs|Au was placed in an ALD chamber to deposit a TiO2 layer (15 cycles). Tetra(dimethylamino)titanium and water were used as precursors during deposition, and the deposition reaction temperature was 80 °C; thus, Si NWs|Au|TiO2 was obtained.

[0080] Photosensitizer P1 and catalyst [Ru(bda)(4-PO3H2-(CH2)3-pyr)2] (ReC) were thoroughly mixed with acetonitrile and methanol under ultrasonication to prepare P1-acetonitrile and ReC-methanol solutions with concentrations of 0.2 mM and 0.2 mM, respectively. A Si NWs|Au-TiO2 electrode was immersed in P1-acetonitrile for 16 h, dried, and then subjected to atomic layer deposition (ALD) of TiO2 on its surface using a precursor for 5 cycles. After immersion in the ReC-acetonitrile solution for 16 h and drying, the Si NWs|Au-TiO2|P1-TiO2|ReC-TiO2 electrode was obtained.

[0081] The prepared photocathode was used for photoelectrocatalytic carbon dioxide reduction:

[0082] Using the prepared photocathode as the working electrode and a platinum sheet as the counter electrode, Ag / Ag + A three-electrode system was constructed as the reference electrode, with an incident light power intensity of 100 mW / cm². 2 Under illumination, carbon dioxide reduction was carried out in a solution containing 0.1 M tetrabutylammonium hexafluorophosphate and acetonitrile, with a voltage of 1.8 V vs Ag / Ag applied to the electrodes. + .

[0083] Figure 1 This is a schematic diagram of the fabrication of a photocathode. Figure 1 It can be seen that the photocathode is mainly composed of Si NWs adsorbing Au NPS, depositing TiO2 thin film through ALD technology to adsorb photosensitizer and catalyst, and coating the outermost layer with TiO2 thin film protective layer.

[0084] Figure 2 The UV absorption spectrum of the Si NWs|Au|TiO2|P1-TiO2|ReC-TiO2 electrode; from Figure 2 It can be seen that the absorption range of the electrode is 500~800 nm, with the maximum absorption wavelength being 670 nm.

[0085] Figure 3 A Faraday effect diagram of CO2 reduction products at the photocathode; from Figure 3 As can be seen from the data, under a bias voltage of -1.8 V, the Faraday efficiency of the product CO was calculated by gas chromatography.

[0086] FE CO It is 72.0%, corresponding to a current of -1.2 mA cm⁻¹. -2 .

[0087] Figure 4 The photocurrent-time curve of the photocathode; from Figure 4It can be seen that under a bias voltage of -1.8 V and continuous illumination, the photocurrent density of the Si NWs|Au|TiO2|P1-TiO2|ReC-TiO2 photocathode decreases by less than 15% within 3 hours, which indicates that the TiO2 protective layer deposited by ALD enhances the stability of the photocathode.

[0088] Figure 5 The Nyquist plot of the photocathode shows that the charge transfer resistance of Si NWs|Au|TiO2-P1-TiO2|-ReC-TiO2 is the lowest at 83.9Ω.

[0089] Example 2

[0090] Si NWs|TiO2-P1-TiO2|ReC-TiO2 photocathode:

[0091] Compared to Example 1, the difference lies in that the Si NWs substrate did not adsorb Au, and the incident light power intensity was 100 mW / cm². 2 Under controlled potential electrolysis in a carbon dioxide atmosphere under continuous simulated illumination (AM 1.5 G), the product CO was quantified by gas chromatography, and the Faraday efficiency was calculated.

[0092] A Si NWs|TiO2-P1-TiO2|ReC-TiO2 photocathode was used for carbon dioxide reduction. Quantification was performed using gas chromatography, and the Faradaic efficiency of the product CO was calculated. The maximum FE was obtained under an applied bias voltage of -1.9 V. CO It is 58.7%.

[0093] Example 3

[0094] Si NWs|0.5Au|TiO2|P1-TiO2|ReC-TiO2 photocathode:

[0095] Compared to Example 1, the difference lies in the preparation method: the Si NWs substrate was immersed in a 0.5 mM HAuCl4 solution, and the oscillation frequency was 120 rpm for 60 min; the incident light power intensity was 100 mW / cm². 2 Under controlled potential electrolysis in a carbon dioxide atmosphere under continuous simulated illumination (AM 1.5 G), the product CO was quantified by gas chromatography, and the Faraday efficiency was calculated.

[0096] Using a Si NWs|0.5Au|TiO2|P1-TiO2|ReC-TiO2 photocathode for carbon dioxide reduction, the maximum CO Faradaic efficiency (FE) was obtained under a bias voltage of -1.9 V. CO It is 62%.

[0097] Example 4

[0098] Si NWs|10Au|TiO2|P1-TiO2|ReC-TiO2 photocathode:

[0099] Compared to Example 1, the difference lies in the preparation method: the Si NWs substrate was immersed in a 0.01 M HAuCl4 solution and shaken (120 rpm) for 60 min; the incident light power intensity was 100 mW / cm. 2 Under controlled potential electrolysis in a carbon dioxide atmosphere under continuous simulated illumination (AM 1.5 G), the product CO was quantified by gas chromatography, and the Faraday efficiency was calculated.

[0100] Using a SiNWs|10Au|TiO2|P1-TiO2|ReC-TiO2 photocathode for carbon dioxide reduction, the maximum carbon monoxide Faraday efficiency (FE) was obtained under an applied bias voltage of -1.9V. CO It is 52.3%.

[0101] Example 5

[0102] Si NWs|Au|TiO2|P1-TiO2|ReC photocathode:

[0103] Compared with Example 1, the difference is that the outermost layer of the Si NWs|Au|TiO2|P1-TiO2|ReC photocathode is not covered with an ALD TiO2 protective layer.

[0104] A Si NWs|Au|TiO2|P1-TiO2|ReC photocathode was used for carbon dioxide reduction at an incident light power intensity of 100 mW / cm². 2 Under illumination conditions, with a bias voltage of -1.8 V applied in a carbon dioxide atmosphere, the photocurrent density decreases by 40% within 1 hour.

[0105] Example 6

[0106] Si NWs|Au|TiO2|P1-TiO2|ReC-TiO2 photocathode:

[0107] A method for fabricating a photocathode based on a silicon nanowire substrate includes the following steps:

[0108] Si NWs were prepared by metal-assisted chemical etching. First, p-type silicon wafers were ultrasonically immersed in acetone, ethanol, and water for 20, 15, and 15 min, respectively, to remove surface impurities. Then, they were further cleaned in H2SO4:H2O2 (v / v, 1:1) solution for 30 min, rinsed with water, and the surface oxide layer was removed in HF solution (5 wt%). The clean silicon wafers were then immersed in solutions containing AgNO3 (0.03 M) and 4.6 M HF for 90 min at room temperature. The silicon wafers were then immersed in HNO3 solution (v / v, 1:1) to remove residual Ag for 45 min. After immersion in HF solution (5 wt%) for 5 min, vertically aligned Si NWs were obtained.

[0109] Si NWs were immersed in HAuCl4 solution (2 mM) and shaken at a frequency of 120 rpm for 60 min. After rinsing with water, a silicon nanowire substrate (Si NWs|Au) with adsorbed Au nanoparticles was obtained.

[0110] Si NWs|Au was placed in an ALD chamber to deposit a TiO2 layer (15 cycles). Tetra(dimethylamino)titanium and water were used as precursors during deposition, and the deposition reaction temperature was 80 °C; thus, Si NWs|Au|TiO2 was obtained.

[0111] Photosensitizer P1 and catalyst [Ru(bda)(4-PO3H2-(CH2)3-pyr)2] (ReC) were thoroughly mixed with acetonitrile and methanol under ultrasonication to prepare P1-acetonitrile and ReC-methanol solutions with concentrations of 0.2 mM and 0.2 mM, respectively. A Si NWs|Au-TiO2 electrode was immersed in P1-acetonitrile for 16 h, dried, and then subjected to atomic layer deposition (ALD) of TiO2 on its surface using a precursor for 5 cycles. After immersion in the ReC-acetonitrile solution for 16 h and drying, the Si NWs|Au-TiO2|P1-TiO2|ReC-TiO2 electrode was obtained.

[0112] The prepared photocathode was used for photoelectrocatalytic carbon dioxide reduction:

[0113] Compared with Example 1, the difference is that the electrolyte solution is replaced with 0.1 M KHCO3 solution;

[0114] A Si NWs|Au|TiO2|P1-TiO2|ReC-TiO2 photocathode was used for carbon dioxide reduction at an incident light power intensity of 100 mW / cm². 2Under the illumination conditions and with a bias voltage of -1.8 V applied in a carbon dioxide atmosphere, photoelectric performance tests were conducted, and it was found that the photocurrent density decreased by less than 15% within 3 hours.

[0115] Example 7

[0116] A method for fabricating a photocathode based on a silicon nanowire substrate includes the following steps:

[0117] Si NWs were prepared by metal-assisted chemical etching. First, p-type silicon wafers were ultrasonically immersed in acetone, ethanol, and water for 20, 15, and 15 min, respectively, to remove surface impurities. Then, they were further cleaned in H2SO4:H2O2 (v / v, 1:1) solution for 20 min, rinsed with water, and the surface oxide layer was removed in HF solution (5 wt%). The clean silicon wafers were then immersed in solutions containing AgNO3 (0.05 M) and 4.3 M HF for 60 min at room temperature. The silicon wafers were then immersed in HNO3 solution (v / v, 1:1) to remove residual Ag for 60 min. After immersion in HF solution (5 wt%) for 10 min, vertically aligned Si NWs were obtained.

[0118] Si NWs were immersed in HAuCl4 solution (0.1 M) and shaken at a frequency of 150 rpm for 90 min. After rinsing with water, a silicon nanowire substrate (Si NWs|Au) with adsorbed Au nanoparticles was obtained.

[0119] Si NWs|Au was placed in an ALD chamber to deposit a TiO2 layer (15 cycles). Tetra(dimethylamino)titanium and water were used as precursors during deposition, and the deposition reaction temperature was 60 °C; thus, Si NWs|Au|TiO2 was obtained.

[0120] Photosensitizer P1 and catalyst [Ru(bda)(4-PO3H2-(CH2)3-pyr)2] (ReC) were thoroughly mixed with acetonitrile and methanol under ultrasonication to prepare solutions with concentrations of 0.3 mM P1-acetonitrile and 0.6 mM ReC-methanol. A Si NWs|Au-TiO2 electrode was immersed in P1-acetonitrile for 16 h, dried, and then subjected to atomic layer deposition (ALD) of TiO2 on its surface using a precursor for 5 cycles. The electrode was then immersed in the ReC-acetonitrile solution for 16 h, dried, and then subjected to ALD of TiO2 on its surface using a precursor for 5 cycles to obtain the Si NWs|Au-TiO2|P1-TiO2|ReC-TiO2 electrode.

[0121] Example 8

[0122] A method for fabricating a photocathode based on a silicon nanowire substrate includes the following steps:

[0123] Si NWs were prepared by metal-assisted chemical etching. First, p-type silicon wafers were ultrasonically immersed in acetone, ethanol, and water for 20, 15, and 15 min, respectively, to remove surface impurities. Then, they were further cleaned in H2SO4:H2O2 (v / v, 1:1) solution for 30 min, rinsed with water, and the surface oxide layer was removed in HF solution (5 wt%). The clean silicon wafers were then immersed in solutions containing AgNO3 (0.03 M) and 4.6 M HF for 90 min at room temperature. The silicon wafers were then immersed in HNO3 solution (v / v, 1:1) to remove residual Ag for 45 min. After immersion in HF solution (5 wt%) for 5 min, vertically aligned Si NWs were obtained.

[0124] Si NWs were immersed in HAuCl4 solution (0.002 M) and shaken at a frequency of 120 rpm for 60 min. After rinsing with water, silicon nanowire substrates (Si NWs|Au) with adsorbed Au nanoparticles were obtained.

[0125] Si NWs|Au was placed in an ALD chamber to deposit a TiO2 layer (15 cycles). Tetra(dimethylamino)titanium and water were used as precursors during deposition, and the deposition reaction temperature was 80 °C; thus, Si NWs|Au|TiO2 was obtained.

[0126] Photosensitizer P1 and catalyst [Ru(bda)(4-PO3H2-(CH2)3-pyr)2] (ReC) were thoroughly mixed with acetonitrile and methanol under ultrasonication to prepare solutions with concentrations of 0.3 mM P1-acetonitrile and 0.5 mM ReC-methanol. A Si NWs|Au-TiO2 electrode was immersed in P1-acetonitrile for 16 h, dried, and then subjected to atomic layer deposition (ALD) of TiO2 on its surface using a precursor for 5 cycles. After immersion in the ReC-acetonitrile solution for 16 h and drying, the Si NWs|Au-TiO2|P1-TiO2|ReC-TiO2 electrode was obtained.

[0127] Example 9

[0128] A method for fabricating a photocathode based on a silicon nanowire substrate includes the following steps:

[0129] Si NWs were prepared by metal-assisted chemical etching. First, p-type silicon wafers were ultrasonically immersed in acetone, ethanol, and water for 20, 15, and 15 min, respectively, to remove surface impurities. Then, they were further cleaned in H2SO4:H2O2 (v / v, 1:1) solution for 30 min, rinsed with water, and the surface oxide layer was removed in HF solution (5 wt%). The clean silicon wafers were then immersed in solutions containing AgNO3 (0.03 M) and 4.6 M HF for 90 min at room temperature. The silicon wafers were then immersed in HNO3 solution (v / v, 1:1) to remove residual Ag for 45 min. After immersion in HF solution (5 wt%) for 5 min, vertically aligned Si NWs were obtained.

[0130] Si NWs were immersed in HAuCl4 solution (2 mM) and oscillated at a frequency of 140 rpm for 80 min. After rinsing with water, a silicon nanowire substrate (Si NWs|Au) with adsorbed Au nanoparticles was obtained.

[0131] Si NWs|Au was placed in an ALD chamber to deposit a TiO2 layer (15 cycles). Tetra(dimethylamino)titanium and water were used as precursors during deposition, and the deposition reaction temperature was 120 °C; thus, Si NWs|Au|TiO2 was obtained.

[0132] Photosensitizer P1 and catalyst [Ru(bda)(4-PO3H2-(CH2)3-pyr)2] (ReC) were thoroughly mixed with acetonitrile and methanol under ultrasonication to prepare solutions with concentrations of 0.3 mM P1-acetonitrile and 0.5 mM ReC-methanol. A Si NWs|Au-TiO2 electrode was immersed in P1-acetonitrile for 16 h, dried, and then subjected to atomic layer deposition (ALD) of TiO2 on its surface using a precursor for 5 cycles. After immersion in the ReC-acetonitrile solution for 16 h and drying, the Si NWs|Au-TiO2|P1-TiO2|ReC-TiO2 electrode was obtained.

[0133] Comparative Example 1

[0134] The photocathode in this comparative example is: Si NWs|Au|TiO2|ReC-TiO2 photocathode;

[0135] Compared to Example 1, the difference lies in that the Si NWs|Au|TiO2|ReC-TiO2 photocathode does not adsorb the P1 photosensitizer, and the incident light power intensity is 100 mW / cm. 2Under controlled potential electrolysis in a carbon dioxide atmosphere under continuous simulated illumination (AM 1.5G), the product CO was quantified by gas chromatography, and the Faraday efficiency was calculated.

[0136] A Si NWs|Au|TiO2|ReC-TiO2 photocathode was used for carbon dioxide reduction. Quantification was performed using gas chromatography, and the Faradaic efficiency of the product CO was calculated. The maximum FE was obtained under an applied bias voltage of -1.9 V. CO It is 43.2%.

[0137] Comparative Example 2

[0138] The photocathode in this comparative example is: Si NWs|TiO2-ReC-TiO2 photocathode;

[0139] Compared to Example 1, the difference lies in that the Si NWs|TiO2-ReC-TiO2 photocathode does not adsorb Au and P1 photosensitizers, and the incident light power intensity is 100 mW / cm. 2 Under controlled potential electrolysis in a carbon dioxide atmosphere under continuous simulated illumination (AM 1.5G), the product CO was quantified by gas chromatography, and the Faraday efficiency was calculated.

[0140] A Si NWs|TiO2-ReC-TiO2 photocathode was used for carbon dioxide reduction. Quantification was performed using gas chromatography, and the Faradaic efficiency of the product CO was calculated. The maximum FE was obtained under an applied bias voltage of -1.9 V. CO It is 14.3%.

[0141] In summary, the Si NWs|Au|TiO2|P1-TiO2|ReC-TiO2 photocathode of this invention exhibits structural stability and excellent photocatalytic performance. The adsorption of Au nanoparticles on the Si NWs substrate leverages the plasmon resonance effect of the metal nanostructure to significantly enhance photo-matter interactions, promoting the catalytic reaction and increasing the selectivity of CO2 reduction. The use of a simple ALD technique to coat the outermost layer with a TiO2 protective layer maintains catalyst stability during the reaction, further enhancing the photocathode structure. The strategy of utilizing the noble metal LSPR effect to improve light absorption can be extended to the efficient conversion of other catalytic systems.

[0142] The method of this invention assembles a photocathode containing photosensitizers and catalysts using atomic layer deposition (ALD) technology, resulting in a stable structure and excellent photoelectrocatalytic performance. This photocathode performs well in photoelectrocatalytic carbon dioxide reduction applications. It eliminates the need for covalent or ionic bonds between photosensitizer / catalyst units to form a photocathode with surface adsorption of photosensitizers and catalysts, leading to a more stable structure and better photoelectrocatalytic performance. The silicon nanowire substrate has a large specific surface area, providing more active sites, which is beneficial for the adsorption of photosensitizers and catalysts, thereby improving the efficiency of the photoelectrocatalytic reaction. By sequentially connecting the photosensitizer and catalyst onto a TiO2 film using ALD and finally coating the TiO2 film, a multilayer structure is formed, which effectively improves the transmission efficiency of photogenerated electrons, reduces charge recombination, and further enhances photoelectrocatalytic performance. ALD deposition of the film adsorbing photosensitizers and catalysts allows for precise nanoscale control, ensuring uniform distribution of photosensitizers and catalysts on the TiO2 film surface, thus improving the stability and activity of the catalyst. Atomic layer deposition (ALD) effectively protects the photosensitizer and catalyst by coating the outermost layer with a TiO2 film, preventing their loss or degradation during the reaction and improving the catalyst's stability and lifespan. ALD is a highly controllable thin-film deposition technique capable of nanoscale precision control, simplifying the traditionally complex photocathode fabrication process and improving reproducibility and consistency. By precisely adsorbing the photosensitizer (P1) and catalyst (ReC) onto the TiO2 film using ALD, a synergistic effect between the photosensitizer and catalyst is achieved, improving the selectivity and efficiency of the CO2 reduction reaction. Optimized multilayer structure design effectively improves the transmission efficiency of photogenerated electrons, reduces charge recombination, and further enhances the efficiency of the CO2 reduction reaction. The photocathode prepared using this technique is suitable for photoelectrocatalytic CO2 reduction reactions, efficiently reducing CO2 to target products (such as CO and HCOOH) under illumination, exhibiting high photoelectrocatalytic efficiency and product selectivity. By constructing a three-electrode system (working electrode, reference electrode, and counter electrode), efficient electrochemical control and reaction monitoring can be achieved in the photoelectrocatalytic CO2 reduction reaction, further improving the stability and controllability of the reaction. The electrolyte solution used in this technology is an acetonitrile solution containing tetrabutylammonium hexafluorophosphate, which exhibits good electrochemical stability and environmental friendliness, making it suitable for long-term photoelectrocatalytic reactions. This technology, through photoelectrocatalytic CO2 reduction, can convert CO2 into the useful chemical fuel CO, demonstrating high sustainability and environmental benefits.

[0143] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for fabricating a photocathode based on a silicon nanowire substrate, characterized in that, Includes the following steps: Au nanoparticles are adsorbed onto the surface of a silicon nanowire substrate to obtain a silicon nanowire substrate with adsorbed Au nanoparticles. The substrate was placed in an atomic layer deposition reaction chamber to deposit a TiO2 film, and then immersed in an acetonitrile solution of P1 photosensitizer for photosensitizer adsorption. After drying, it was placed in an atomic layer deposition reaction chamber to deposit a TiO2 film, and then immersed in a methanol solution of ReC catalyst for catalyst adsorption. Finally, the TiO2 film was coated by atomic layer deposition to obtain a photocathode based on a silicon nanowire substrate. The photosensitizer is a P1 photosensitizer, and the P1 photosensitizer is 4-(Bis-{4-[5-(2,2-dicyano-vinyl)-thiophene-2-yl]-phenyl}-amino)-benzoic acid; The catalyst is a ReC catalyst, and the ReC catalyst is [Ru(bda)(4-PO3H2-(CH2)3-pyr)2] catalyst.

2. The method for fabricating a photocathode based on a silicon nanowire substrate according to claim 1, characterized in that, The method for preparing the silicon nanowire substrate is as follows: After processing the silicon wafer, a silicon wafer is obtained. The silicon wafer is then immersed in AgNO3 solution for 60-90 min and HF solution for 60-90 min in sequence, and then immersed in HNO3 solution for 60-90 min and HF solution for 5-10 min in sequence to obtain a silicon nanowire substrate. The steps for processing the silicon wafer are as follows: The silicon wafer was then washed in a mixed solution of H2SO4 and H2O2 at a volume ratio of 1:1 for 20-40 minutes to obtain the wafer. The concentrations of the AgNO3 solution and the HF solution were 0.03~0.05 M and 4.3~4.6 M, respectively.

3. The method for fabricating a photocathode based on a silicon nanowire substrate according to claim 1, characterized in that, Au nanoparticles are adsorbed onto the surface of a silicon nanowire substrate by immersing the silicon nanowire substrate in a HAuCl4 solution and then oscillating it; the concentration of the HAuCl4 solution is 0.002~0.1 M.

4. The method for fabricating a photocathode based on a silicon nanowire substrate according to claim 3, characterized in that, The oscillation frequency is 120~150 rpm, and the duration is 60~90 min.

5. The method for fabricating a photocathode based on a silicon nanowire substrate according to claim 1, characterized in that, The specific steps for depositing a TiO2 thin film on a silicon nanowire substrate using atomic layer deposition are as follows: A silicon nanowire substrate was placed in a deposition chamber, and a deposition reaction was carried out using tetra(dimethylamino)titanium and water as precursors to form a TiO2 film on the surface of the silicon nanowire substrate. The deposition reaction temperature of the tetra(dimethylamino)titanium is 60~120 ℃.

6. The method for fabricating a photocathode based on a silicon nanowire substrate according to claim 5, characterized in that, The TiO2 film was deposited on the silicon nanowire substrate for 15 cycles.

7. The method for fabricating a photocathode based on a silicon nanowire substrate according to claim 1, characterized in that, After being soaked in an acetonitrile solution of P1 photosensitizer and dried, TiO2 was grown on its surface by atomic layer deposition using a precursor for 5 cycles. Then, it was taken out, soaked in a methanol solution of ReC catalyst and dried, and TiO2 was grown on its surface by atomic layer deposition using a precursor for 5 cycles. The concentration of the acetonitrile solution of the P1 photosensitizer is 0.2~0.3 mM; the concentration of the methanol solution of the ReC catalyst is 0.2~0.6 mM.

8. The method for fabricating a photocathode based on a silicon nanowire substrate according to claim 1, characterized in that, The specific steps for coating TiO2 thin films using atomic layer deposition are as follows: TiO2 thin films were deposited using tetra(dimethylamino)titanium and water as precursors to obtain photocathodes based on silicon nanowire substrates; The TiO2 thin film was deposited in 5 cycles.

9. A photocathode based on a silicon nanowire substrate, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

10. The application of the silicon nanowire-based photocathode as described in claim 9 in photoelectrocatalytic carbon dioxide reduction, characterized in that, Includes the following steps: Using a silicon nanowire-based photocathode as the working electrode, Ag / Ag + A three-electrode system was constructed using a reference electrode and a platinum sheet as the counter electrode. Photoelectrocatalytic carbon dioxide reduction was carried out in the electrolyte solution of the three-electrode system. The incident light power intensity of the light source used in the photoelectrocatalytic carbon dioxide reduction reaction is 100 mW / cm². 2 The applied bias voltage range is -1.3 to -1.9 V; The electrolyte solution is an acetonitrile solution containing 0.1 M tetrabutylammonium hexafluorophosphate.

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