Photo-anode based on acid etching surface reconstruction and preparation method thereof

Abstract

The invention discloses a photo-anode based on acid etching surface reconstruction and a preparation method thereof, and relates to the technical field of photoelectrochemistry. The preparation method comprises the following steps: S1, preparing a prismatic transition metal sulfide nanorod array on a cleaned conductive substrate to obtain a conductive substrate loaded with the prismatic transition metal sulfide nanorod array; and S2, acid etching is carried out on the conductive substrate loaded with the prismatic transition metal sulfide nanorod array in the step S1, the prismatic transition metal sulfide nanorod array is reconstructed into a cylindrical transition metal sulfide nanorod array, and the photo-anode based on acid etching surface reconstruction is obtained. After the prepared photoanode is subjected to acid etching surface reconstruction, the surface catalytic performance is obviously improved, the photocurrent density of an optimized sample under the bias voltage of 1.23 VRHE can reach 2.57 mA / cm < 2 > and is 2.89 times that of an original sample, and the photoanode has high photoelectrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of photoelectrochemical technology and relates to a photoanode based on acid-etched surface reconstruction and its preparation method. Background Technology

[0002] Photoelectrochemical (PEC) water splitting for hydrogen production can directly convert solar energy into hydrogen energy. However, the low visible light utilization rate and rapid carrier recombination limit the development of PEC water splitting hydrogen production technology. A typical PEC water splitting hydrogen production system consists of three parts: a photoanode, a photocathode, and an electrolyte. The photoanode involves a four-electron reaction and is the rate-determining step of the entire reaction. Therefore, improving the photoelectric conversion efficiency of the photoanode can effectively improve the solar-to-hydrogen conversion efficiency, achieving efficient energy utilization.

[0003] Transition metal sulfides are widely used as photoanode materials due to their narrow band gaps, suitable band positions, and excellent surface photoelectric properties. However, severe bulk carrier recombination and poor surface carrier injection hinder their development in the field of photoelectrochemical oxidation (PEC). Existing technologies utilize strategies such as heterojunction construction, elemental doping, and structural engineering to improve the carrier concentration and promote bulk carrier separation in transition metal sulfide photoanodes. Among these, the surface tip effect of the photoanode induces local enhancement of PEC-related physical quantities such as electric field, optical field, and carrier transport, which helps improve the surface catalytic performance of the photoanode. However, the surface tip effect in the PEC field is not without its negative effects; improper structural design can lead to adverse effects. For example, in cadmium sulfide (CdS) hexagonal prism nanorod photoanodes, insufficient tip effect at the side edges prevents the formation of a uniform local field and active site distribution, resulting in poor surface catalytic activity and slow water oxidation kinetics on the photoanode surface. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to overcome the problem of low surface carrier injection efficiency in existing photoanodes loaded with prismatic transition metal sulfide nanorod arrays due to insufficient edge tip effect, and to provide a photoanode based on acid etching surface reconstruction and its preparation method.

[0005] Technical solution: The present invention provides a method for preparing a photoanode based on acid etching surface reconstruction, comprising the following steps: S1. Prepare a prismatic transition metal sulfide nanorod array on a cleaned conductive substrate to obtain a conductive substrate loaded with a prismatic transition metal sulfide nanorod array. S2. Acid etching is performed on the conductive substrate loaded with the prismatic transition metal sulfide nanorod array described in step S1 to reconstruct the prismatic transition metal sulfide nanorod array into a cylindrical transition metal sulfide nanorod array, thereby obtaining a photoanode based on the acid-etched surface reconstruction.

[0006] This invention employs a simple targeted acid etching strategy to modify the lateral edges of prismatic transition metal sulfide nanorod arrays, alleviating the surface carrier accumulation problem caused by insufficient tip effect and accelerating the water oxidation reaction kinetics on the photoanode surface. Simultaneously, the sulfur vacancies formed in situ during acid etching broaden the light absorption band tail of the transition metal sulfide photoanode, enhancing its visible light capture capability. Ultimately, this invention optimizes the PEC performance of the transition metal sulfide photoanode by modulating the molecular structure of the photoanode surface through acid etching.

[0007] Furthermore, the transition metal sulfide is one or more of CdS, ZnS, or CdIn2S4.

[0008] Further, in step S1, the cleaning step involves ultrasonically cleaning the conductive substrate in acetone, alcohol, and water for 30 minutes each.

[0009] Furthermore, the conductive substrate is fluorine-doped tin oxide conductive glass.

[0010] Further, in step S1, the preparation of the conductive substrate loaded with prismatic transition metal sulfide nanorod arrays includes the following steps: immersing the cleaned conductive substrate in a hydrothermal precursor solution and reacting it at 100-180 °C for 1-6 h to obtain the conductive substrate loaded with prismatic transition metal sulfide nanorod arrays; the hydrothermal precursor solution is obtained by dissolving transition metal salts and sulfur sources in water.

[0011] Further, in step S2, the preparation method of the photoanode based on acid-etched surface reconstruction includes the following steps: immersing the conductive substrate loaded with prismatic transition metal sulfide nanorod arrays as described in step S1 into an acidic etching solution and reacting it at 50-90 °C for 10-30 min to obtain the photoanode based on acid-etched surface reconstruction; the acidic etching solution is obtained by dissolving bismuth iodide and hydrochloric acid in an alcohol solution, and the amount of hydrochloric acid added makes the pH value of the acidic etching solution between 2 and 3.

[0012] Another objective of this invention is to provide a photoanode based on acid-etched surface reconstruction, which is prepared by the above-described method for preparing a photoanode based on acid-etched surface reconstruction. The photoanode based on acid-etched surface reconstruction includes a conductive substrate, and the surface of the conductive substrate is loaded with an array of cylindrical transition metal sulfide nanorods.

[0013] Furthermore, the cylindrical transition metal sulfide nanorods have a diameter of 100-200 nm.

[0014] Furthermore, the cylindrical transition metal sulfide nanorods have a height of 1-2 μm.

[0015] Beneficial effects: (1) The photoanode based on acid etching surface reconstruction of the present invention transforms the prismatic nanorod array of the photoanode into a cylindrical nanorod array through acid etching, which effectively alleviates the problem of surface charge carrier accumulation caused by insufficient tip effect, while accelerating the oxygen evolution reaction kinetics on the photoanode surface and improving the photoelectrochemical performance of the photoanode.

[0016] (2) The photoanode based on acid-etched surface reconstruction of the present invention has a high carrier injection efficiency, indicating that acid-etched surface reconstruction is beneficial to optimizing the carrier transport path on the photoanode surface and improving the catalytic performance of the photoanode surface. By rationally controlling the molecular structure of the photoanode surface, optimizing the carrier transport path on the photoanode surface, promoting surface carrier injection, and improving the photoelectrochemical performance of the photoanode.

[0017] (3) The photoanode based on acid-etched surface reconstruction of the present invention significantly improves the photocurrent density, and the optimized sample at 1.23 V RHE The photocurrent density under bias voltage can reach 2.57 mA / cm². 2 The carrier separation efficiency reached 43.20%, and the injection efficiency reached 65.76%.

[0018] (4) The method for preparing photoanodes based on acid etching surface reconstruction of the present invention has the advantages of simple procedure, sufficient raw materials and low price, which is conducive to large-scale production and has great potential application value. Attached Figure Description

[0019] Figure 1 (a) is a SEM (scanning electron microscope) image of the photoanode structure of Embodiment 1 of the present invention; Figure 1 (b) is a SEM (scanning electron microscope) image of the photoanode structure in Comparative Example 1.

[0020] Figure 2 The LSV (linear sweep current-voltage characteristic) curves of the photoanodes in Embodiment 1 and Comparative Example 1 of the present invention are shown. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] Example 1

[0023] A method for fabricating a photoanode based on acid-etched surface reconstruction specifically includes the following steps: (1) The tin oxide conductive glass (FTO) substrate was ultrasonically cleaned for 30 min each in acetone, alcohol and ultrapure water.

[0024] (2) Dissolve 2 mmol of cadmium nitrate powder and 2 mmol of thiourea powder in 100 mL of ultrapure water and stir for 20 min to obtain a clear hydrothermal precursor solution. Place the washed FTO substrate tilted in a 25 mL polytetrafluoroethylene container with the conductive side facing down, and take 10 mL of the above precursor solution for hydrothermal reaction. Control the hydrothermal reaction temperature at 180 ℃, the heating time at 20 min, and the holding time at 6 h to obtain a cadmium sulfide (CdS) nanorod array with a thickness of 1.5 μm. Place the obtained CdS nanorod array in a vacuum drying oven at 60 ℃ for 24 h for further processing.

[0025] (3) Dissolve 0.295 g of bismuth iodide powder in 50 mL of ethanol solution, and add 125 μL of 38% hydrochloric acid to adjust the pH of the solution to 2.5 to obtain an acidic etching solution. Place the conductive substrate with cadmium sulfide nanorod arrays obtained in step (2) in a 100 mL glass dish with the CdS side facing up, and take 50 mL of the above acidic etching solution for reaction. Control the reaction temperature at 60 ℃ and the reaction time at 30 min to obtain the photoelectrochemical photoanode with the desired surface reconstruction.

[0026] The photoelectrochemical photoanode prepared using this method operates at 1.23 V. RHE Under bias voltage, the photocurrent density is 2.57 mA / cm². 2 It is 2.89 times that of the original sample, with a carrier separation efficiency of 43.20% and an injection efficiency of 65.76%.

[0027] Example 2

[0028] A CdS nanorod array was prepared on a conductive substrate according to the methods in steps (1) and (2) of Example 1, except for step (3): (3) Dissolve 0.295 g of bismuth iodide powder in 50 mL of ethanol solution, and add 125 μL of 38% hydrochloric acid to adjust the pH of the solution to 2.5 to obtain an acidic etching solution. Place the conductive substrate with cadmium sulfide nanorod array obtained in step (2) in a 100 mL glass dish with the CdS side facing up, and take 50 mL of the above acidic etching solution for reaction. Control the reaction temperature at 50 °C and the reaction time at 30 min to obtain Example 2.

[0029] The photoelectrochemical photoanode prepared using this method operates at 1.23 V. RHE Under bias voltage, the photocurrent density is 1.59 mA / cm². 2 .

[0030] Example 3

[0031] A CdS nanorod array was prepared on a conductive substrate according to the methods in steps (1) and (2) of Example 1, except for step (3): (3) Dissolve 0.295 g of bismuth iodide powder in 50 mL of ethanol solution, and add 125 μL of 38% hydrochloric acid to adjust the pH of the solution to 2.5 to obtain an acidic etching solution. Place the conductive substrate with cadmium sulfide nanorod array obtained in step (2) in a 100 mL glass dish with the CdS side facing up, and take 50 mL of the above acidic etching solution for reaction. Control the reaction temperature at 90 °C and the reaction time at 30 min to obtain Example 3.

[0032] The photoelectrochemical photoanode prepared using this method operates at 1.23 V. RHE Under bias voltage, the photocurrent density is 1.38 mA / cm². 2 .

[0033] Example 4

[0034] A CdS nanorod array was prepared on a conductive substrate according to the methods in steps (1) and (2) of Example 1, except for step (3): (3) Dissolve 0.295 g of bismuth iodide powder in 50 mL of ethanol solution, and add 125 μL of 38% hydrochloric acid to adjust the pH of the solution to 2.5 to obtain an acidic etching solution. Place the conductive substrate with cadmium sulfide nanorod array obtained in step (2) in a 100 mL glass dish with the CdS side facing up, and take 50 mL of the above acidic etching solution for reaction. Control the reaction temperature at 60 °C and the reaction time at 10 min to obtain Example 4.

[0035] The photoelectrochemical photoanode prepared using this method operates at 1.23 V. RHE Under bias voltage, the photocurrent density is 1.48 mA / cm². 2 .

[0036] Example 5

[0037] Prepare and modify the conductive substrate according to the methods in steps (1) and (3) of Example 1, except for step (2): (2) Dissolve 1 mmol of cadmium nitrate powder, 2 mmol of indium nitrate, and 4 mmol of thiourea powder in 100 mL of ultrapure water and stir for 20 min to obtain a clear hydrothermal precursor solution. Place the washed FTO substrate tilted in a 25 mL polytetrafluoroethylene container with the conductive side facing down, and take 10 mL of the above precursor solution for hydrothermal reaction. Control the hydrothermal reaction temperature at 200 °C, the heating time at 20 min, and the holding time at 4 h to obtain a CdIn2S4 nanoarray with a thickness of 1.5 μm. Place the obtained CdIn2S4 nanoarray in a vacuum drying oven at 60 °C for 24 h for further processing.

[0038] The photoelectrochemical photoanode prepared using this method operates at 1.23 V. RHE Under bias voltage, the photocurrent density is 1.40 mA / cm². 2 .

[0039] Comparative Example 1 CdS nanorod arrays were prepared on a conductive substrate according to the methods in steps (1) and (2) of Example 1, except that step (3) was not performed.

[0040] The photoelectrochemical photoanode prepared using this method operates at 1.23 V. RHE Under bias voltage, the photocurrent density is 0.88 mA / cm². 2 .

[0041] Comparative Example 2 A CdS nanorod array was prepared on a conductive substrate according to the methods in steps (1) and (2) of Example 1, except for step (3): (3) Dissolve 0.295 g of bismuth iodide powder in 50 mL of ethanol solution, and add 125 μL of 38% hydrochloric acid to adjust the pH of the solution to 2.5 to obtain an acidic etching solution. Place the conductive substrate with cadmium sulfide nanorod array obtained in step (2) in a 100 mL glass dish with the CdS side facing up, and take 50 mL of the above acidic etching solution for reaction. Control the reaction temperature at 60 °C and the reaction time at 50 min to obtain Example 5.

[0042] The photoelectrochemical photoanode prepared using this method operates at 1.23 V. RHE Under bias voltage, the photocurrent density is 0.59 mA / cm². 2 .

[0043] Test Example 1 The photoanodes of Example 1 and Comparative Example 1 were characterized by scanning electron microscopy, and the results are as follows: Figure 1 As shown. Figure 1As shown in (a), the original CdS photoanode of Comparative Example 1 is a hexagonal prism nanoarray, as... Figure 1 As shown in (b), the CdS nanorod array is cylindrical after acid etching, indicating that acid etching caused a change in the surface morphology of the prismatic CdS photoanode.

[0044] Test Example 2 The photocurrent density of the photoanodes prepared in Example 1 and Comparative Example 1 was measured, and the results are as follows: Figure 2 As shown.

[0045] from Figure 2 As can be seen, due to the optimization of the carrier injection path on the photoanode surface by surface reconstruction, the photoelectrochemical performance of the sample in Example 1 is greatly improved compared with that of Comparative Example 1.

Claims

1. A method for preparing a photoanode based on acid-etched surface reconstruction, characterized in that, Includes the following steps: S1. Prepare a prismatic transition metal sulfide nanorod array on a cleaned conductive substrate to obtain a conductive substrate loaded with a prismatic transition metal sulfide nanorod array. S2. Acid etching is performed on the conductive substrate loaded with the prismatic transition metal sulfide nanorod array described in step S1 to reconstruct the prismatic transition metal sulfide nanorod array into a cylindrical transition metal sulfide nanorod array, thereby obtaining a photoanode based on the acid-etched surface reconstruction.

2. The method for preparing a photoanode based on acid-etched surface reconstruction according to claim 1, characterized in that, The transition metal sulfide is one or more of CdS, ZnS, or CdIn2S4.

3. The method for preparing a photoanode based on acid-etched surface reconstruction according to claim 1, characterized in that, In step S1, the cleaning step involves ultrasonically cleaning the conductive substrate in acetone, alcohol, and water for 30 minutes each.

4. The method for preparing a photoanode based on acid-etched surface reconstruction according to any one of claims 1-3, characterized in that, The conductive substrate is fluorine-doped tin oxide conductive glass.

5. The method for preparing a photoanode based on acid-etched surface reconstruction according to claim 1, characterized in that, In step S1, the preparation of the conductive substrate loaded with prismatic transition metal sulfide nanorod arrays includes the following steps: immersing the cleaned conductive substrate in a hydrothermal precursor solution and reacting it at 100-180 °C for 1-6 h to obtain the conductive substrate loaded with prismatic transition metal sulfide nanorod arrays; the hydrothermal precursor solution is obtained by dissolving transition metal salts and sulfur sources in water.

6. The method for preparing a photoanode based on acid-etched surface reconstruction according to claim 5, characterized in that, The sulfur source is one or more of thioacetamide, thiourea, and L-cysteine.

7. The method for preparing a photoanode based on acid etching surface reconstruction according to claim 1, characterized in that, In step S2, the preparation method of the photoanode based on acid-etched surface reconstruction includes the following steps: immersing the conductive substrate loaded with prismatic transition metal sulfide nanorod arrays as described in step S1 into an acidic etching solution and reacting it at 50-90 °C for 10-30 min to obtain the photoanode based on acid-etched surface reconstruction; the acidic etching solution is obtained by dissolving bismuth iodide and hydrochloric acid in an alcohol solution, and the amount of hydrochloric acid added makes the pH value of the acidic etching solution between 2 and 3.

8. A photoanode based on acid-etched surface reconstruction, characterized in that, The photoanode based on acid-etched surface reconstruction is prepared by any one of the preparation methods described in claims 1-7, and includes a conductive substrate on which a cylindrical transition metal sulfide nanorod array is loaded.

9. The photoanode based on acid-etched surface reconstruction according to claim 8, characterized in that, The cylindrical transition metal sulfide nanorods have a diameter of 100-200 nm.

10. The photoanode based on acid-etched surface reconstruction according to claim 8, characterized in that, The cylindrical transition metal sulfide nanorods have a height of 1-2 μm.

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