zincln2s4 / nifeohh-s thin film electrode

Abstract

The ZnIn2S4 / NiFeOOH-S thin film electrode is prepared by the following method: InCl3, ZnCl2 and thiourea are dissolved in an aqueous ethylene glycol solution to form a reaction solution; a conductive substrate is placed in the reaction solution for a closed solvothermal reaction to form a ZnIn2S4 thin film on the conductive surface of the substrate; the substrate with the ZnIn2S4 thin film is subjected to annealing treatment; a NiFeOOH layer is electrolytically deposited on the ZnIn2S4 thin film of the substrate; and the substrate with the ZnIn2S4 / NiFeOOH is subjected to immersion treatment in an immersion solution containing Na2S and Na2SO3 to obtain the ZnIn2S4 / NiFeOOH-S thin film electrode. The thin film electrode according to the application can stably and obviously perform photoelectrocatalysis on the sulfur oxidation reaction.

Description

Technical Field

[0001] This invention relates to a thin-film electrode for photoelectrocatalytic sulfur oxidation. Background Technology

[0002] In applications such as photoelectrocatalytic water splitting or photoelectrocatalytic degradation of organic pollutants in wastewater, photoelectrodes with photoelectrocatalytic properties are required, such as the indium sulfide-based thin-film electrode disclosed in CN114751655A. However, since sulfur oxidation is an electrochemical oxidation reaction with a lower theoretical potential than water oxidation, such existing indium sulfide-based thin-film electrodes are not suitable for sulfur oxidation catalysis. Summary of the Invention

[0003] The purpose of this invention is to provide an indium zinc sulfide-based composite thin film electrode with excellent photoelectrocatalytic sulfur oxidation performance.

[0004] According to a first aspect of the present invention, a method for preparing a ZnIn2S4 / NiFeOOH-S thin film electrode is provided, comprising:

[0005] Provides a clean conductive substrate;

[0006] Provide an aqueous solution of ethylene glycol;

[0007] InCl3, ZnCl2, and thiourea are dissolved in an aqueous ethylene glycol solution to form a reaction solution;

[0008] The substrate is placed in a reaction solution for a closed solvothermal reaction to form a ZnIn2S4 thin film on the conductive surface of the substrate.

[0009] The substrate with the ZnIn2S4 thin film formed was annealed.

[0010] A NiFeOOH layer was electrolytically deposited on a ZnIn2S4 thin film substrate, wherein the electrolyte used contained Ni(NO3)2 and Fe(NO3)3;

[0011] Provide an immersion solution containing Na2S and Na2SO3;

[0012] The ZnIn2S4 / NiFeOOH-S thin film electrode is obtained by immersing the substrate with the ZnIn2S4 / NiFeOOH formation in an immersion solution.

[0013] The conductive substrate according to the present invention can be an FTO conductive glass planar substrate, which has at least one conductive surface. The substrate is preferably placed at an angle (forming an angle of, for example, 30 degrees) in the reaction solution, with the conductive surface facing down and the non-conductive surface facing up.

[0014] According to the present invention, the volume ratio of ethylene glycol to water in the ethylene glycol aqueous solution can be 1:4 to 1:6, preferably 1:5.

[0015] According to the present invention, the molar concentrations of zinc ions, indium ions, and sulfide ions in the reaction solution are 0.01 mol / L, 0.02 mol / L, and 0.04 mol / L, respectively. Furthermore, the metal salt in the reaction solution can also be in hydrate form, such as InCl3·4H2O.

[0016] According to the present invention, the molar concentrations of nickel ions and iron ions in the electrolyte are both 0.1 mol / L. Furthermore, electrolytic deposition can be performed using a three-electrode system with cyclic voltammetry (CV), for example, a voltage range of 0.2 V to -1.2 V, a scan rate of 100 mV / s, and 5-20 scan cycles. Additionally, the nickel and iron salts in the electrolyte can also be in their hydrated form.

[0017] According to the present invention, the soaking solution contains 0.25M Na₂S and 0.35M Na₂SO₃. This soaking solution can be further used as the corresponding electrolyte solution in subsequent electrode performance tests. The inventors accidentally discovered during experiments that the catalyst phase of the ZnIn₂S₄ / NiFeOOH thin film layer soaked in this electrolyte solution can be altered to generate a new phase, NiFeOOH-S, with significantly improved photoelectrocatalytic sulfur oxidation performance in situ. During soaking, the substrate is preferably placed vertically in the soaking solution, and the soaking time is approximately 1 hour.

[0018] According to the present invention, the temperature of the solvothermal reaction can be 150-170°C, and the time can be 5.5-6.5 hours; the reaction temperature can be further preferably 160°C, and the reaction time can be further preferably 6 hours.

[0019] According to the present invention, in the annealing process, the preferred annealing temperature is 350℃~450℃, and the annealing time is 0.5~1.5 hours; more preferably, the annealing temperature is 400℃, and the annealing time is 1 hour. Annealing can improve the crystallinity of ZnIn2S4 thin film material so that it has a better carrier migration path and enhances its photoelectrochemical catalytic performance.

[0020] Alternatively, the substrate can be naturally cooled to room temperature before annealing, and then cleaned and vacuum dried.

[0021] According to a second aspect of the invention, an electrode for photoelectrocatalytic sulfur oxidation is also provided, which is made by the method described above.

[0022] According to the thin-film electrode of the present invention, stable chemical bonds can be formed between NiFeOOH-S and ZnIn2S4, thereby ensuring stable catalyst performance. Furthermore, the in-situ generated NiFeOOH-S exhibits significant photoelectrocatalytic activity in the sulfur oxidation reaction.

[0023] The preparation process of this invention is simple, the conditions are mild, the reaction time is short, the morphology and size of the product are well controllable, and the repeatability is high. Attached Figure Description

[0024] Figure 1a and Figure 1b Transmission electron microscopy (TEM) images of the ZnIn2S4 / NiFeOOH-S catalyst thin films prepared according to embodiments of the present invention at different resolutions;

[0025] Figure 2 A scanning electron microscope image of the ZnIn2S4 / NiFeOOH-S catalyst film prepared according to an embodiment of the present invention;

[0026] Figure 3 Linear sweep voltammetry (LSV) curves of the ZnIn2S4 / NiFeOOH-S catalyst film and the ZnIn2S4 catalyst film prepared according to embodiments of the present invention are shown in the figure.

[0027] Figure 4 The current-time curves of the ZnIn2S4 / NiFeOOH-S catalyst film and the ZnIn2S4 catalyst film prepared according to embodiments of the present invention are shown.

[0028] Figure 5 Raman spectra of ZnIn2S4 / NiFeOOH(-S) catalyst films at different reaction times. Detailed Implementation

[0029] The present invention will be further described below with reference to the embodiments and accompanying drawings. Those skilled in the art should understand that the embodiments and accompanying drawings are only for a better understanding of the present invention and are not intended for any limiting purpose.

[0030] Example

[0031] Clean and dry the FTO conductive glass flat substrate for later use. Soak the inner liner of the reactor in dilute nitric acid solution for 12 hours, then clean and dry it for later use.

[0032] Ethylene glycol and water were mixed at a volume ratio of 1:5 to obtain 30 ml of mixed solvent;

[0033] Dissolve 0.0409g ZnCl2, 0.1759g InCl3·4H2O, and 0.0913g thiourea in the above mixed solvent to form a reaction solution. Stir the reaction solution vigorously at room temperature for 10 minutes to ensure complete dissolution.

[0034] A conductive glass substrate is placed at an angle in the reaction solution, with the conductive surface of the substrate facing down and the non-conductive surface facing up, and the substrate forming a 30-degree angle with the vertical plane.

[0035] A closed solvothermal reaction was carried out on the reaction solution containing the substrate at a temperature of 160°C for 6 hours.

[0036] After the reaction was completed, the substrate on which the ZnIn2S4 thin film was formed was naturally cooled to room temperature.

[0037] Clean and cool the substrate, then vacuum dry for 12 hours;

[0038] The ZnIn2S4 thin film was annealed in a muffle furnace at a temperature of 400℃ for 1 hour.

[0039] Dissolve 0.872g Ni(NO3)2·6H2O in 30 mL of water and 0.404g Fe(NO3)3·9H2O in 10 mL of water. Take 24 mL of the solution and 6 mL of the solution respectively and mix them to form an electrolyte.

[0040] A three-electrode system, consisting of an FTO substrate with a ZnIn2S4 thin film as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode, was used to perform CV cyclic voltammetry electrodeposition of a NiFeOOH layer in a prepared electrolyte. The voltage range was 0.2V to -1.2V, the scan rate was 100mV / s, and the number of scan cycles was 10.

[0041] The ZnIn2S4 / NiFeOOH, which was dried in a vacuum oven, was vertically immersed in a mixed solution of 0.25M Na2S and 0.35M Na2SO3 for 1 hour to obtain the target product ZnIn2S4 / NiFeOOH-S.

[0042] TEM image analysis of ZnIn2S4 / NiFeOOH-S thin films

[0043] Figure 1a This is a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image of the ZnIn2S4 / NiFeOOH-S thin film prepared according to the examples. Figure 1bThe image shows a high-resolution transmission electron microscope (HRTEM) image. It can be seen from the image that both ZnIn2S4 and NiFeOOH-S exhibit good crystallinity. The 0.305 nm lattice fringes belong to the crystal planes of ZnIn2S4, and the 0.314 nm lattice fringes belong to the crystal planes of NiFeOOH-S, indicating the presence and good crystallinity of NiFeOOH-S generated in situ on ZnIn2S4. The in-situ SOR sulfur oxidation reaction mainly benefits from the formation of the new substance NiFeOOH-S.

[0044] SEM image analysis of ZnIn2S4 / NiFeOOH-S catalyst film

[0045] Figure 2 SEM images of the ZnIn2S4 / NiFeOOH-S thin films prepared according to the examples are shown. Figure 2 It can be clearly observed that a large number of flocculent NiFeOOH-S are uniformly dispersed on ZnIn2S4 nanosheets, indicating that NiFeOOH-S has successfully and stably attached to ZnIn2S4 nanosheets to form a composite structure.

[0046] LSV performance testing of ZnIn2S4 / NiFeOOH-S catalyst films

[0047] Figure 3 In a three-electrode system, the ZnIn2S4 / NiFeOOH-S thin film electrode and the ZnIn2S4 thin film electrode prepared according to the examples were used as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode. Linear sweep voltammetry (LSV) was performed in 30 mL of 0.25 M Na2S and 0.35 M Na2SO3 electrolyte solutions. At a voltage of 1.4 V vs. RHE, the photocurrent density of ZnIn2S4 was only 1.5 mA / cm². 2 The photocurrent density of ZnIn2S4 / NiFeOOH-S can be rapidly increased to 6.5 mA / cm². 2 This is superior to many currently reported ZnIn2S4-based catalysts. The reason is that the in-situ generated NiFeOOH-S undergoes a sulfur oxidation reaction (SOR) in 0.25M Na2S and 0.35M Na2SO3 electrolyte solutions. The sulfur oxidation reaction (-0.48V vs. RHE) has a lower theoretical potential than the water oxidation reaction (1.23V vs. RHE).

[0048] It performance testing of ZnIn2S4 / NiFeOOH-S catalyst films

[0049] Figure 4In a three-electrode system, the ZnIn2S4 / NiFeOOH-S thin film electrode and the ZnIn2S4 thin film electrode prepared according to the examples were used as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode, respectively. Current-time measurements were performed in 30 mL of 0.25 M Na2S and 0.35 M Na2SO3 electrolyte solutions. At a constant voltage of 0.6 V vs. RHE, the photocurrent density of ZnIn2S4 completely decayed to 0 in less than 2 hours, while the photocurrent density of ZnIn2S4 / NiFeOOH-S reached its peak at 6 hours, gradually decreased over the next 6 hours, but still retained more than 70% of the photocurrent density after 12 hours. This indicates that ZnIn2S4 / NiFeOOH-S can effectively and significantly improve the stability of ZnIn2S4-based catalysts. The reason is that after the introduction of NiFeOOH cocatalyst, it will form bonds with S on the surface of ZnIn2S4, stabilizing the S that is severely photocorroded. A stable electron channel is formed between ZnIn2S4 and NiFeOOH-S, which effectively accelerates electron transport. Furthermore, as the reaction time is extended, the degree of in-situ activation of NiFeOOH continuously increases, and more NiFeOOH-S participates in the sulfur oxidation reaction, making the photoelectrocatalytic effect more obvious.

[0050] Raman spectroscopy analysis of ZnIn2S4 / NiFeOOH-S catalyst film

[0051] To further investigate the stepwise oxidation mechanism of SOR using Raman spectroscopy, such as... Figure 5 As shown, the Raman spectrum of ZnIn2S4 / NiFeOOH before soaking (0h in the figure) was first measured as a control. Then, it was soaked in 0.25M Na2S and 0.35M Na2SO3 electrolyte solution for 1 hour. After reacting for 2 hours under a three-electrode system with an external constant potential of 0.6V vs RHE, the characteristic peak of S8 appeared at 146 cm⁻¹. -1 216cm -1 416cm -1 At 146 cm⁻¹, the characteristic peak was present, but its intensity was not high, and other S intermediate peaks were also present. However, as the reaction time was extended to 4 h, the characteristic peak of S8 remained at 146 cm⁻¹. -1 216cm -1 416cm -1 However, the characteristic peak intensity increased sharply, and there were basically no other characteristic peaks of S intermediate products, indicating that all S intermediate products were converted into S8 and a large amount of S8 was attached to the electrode surface, proving that the SOR sulfur oxidation reaction occurred.

Claims

1. A method for preparing a ZnIn2S4 / NiFeOOH-S thin film electrode, comprising: Provides a clean conductive substrate; Provide an aqueous solution of ethylene glycol; InCl3, ZnCl2, and thiourea are dissolved in an aqueous ethylene glycol solution to form a reaction solution; The substrate is placed in a reaction solution for a closed solvothermal reaction to form a ZnIn2S4 thin film on the conductive surface of the substrate. The substrate with the ZnIn2S4 thin film formed was annealed. A NiFeOOH layer was electrolytically deposited on a ZnIn2S4 thin film substrate, wherein the electrolyte used contained Ni(NO3)2 and Fe(NO3)3; Provide an immersion solution containing Na2S and Na2SO3; The ZnIn2S4 / NiFeOOH-S thin film electrode is obtained by immersing the substrate with the ZnIn2S4 / NiFeOOH formation in an immersion solution.

2. According to the preparation method of claim 1, the volume ratio of ethylene glycol to water in the ethylene glycol aqueous solution is 1:4 to 1:

6.

3. According to the preparation method of claim 1, the molar ratio of zinc ions, indium ions and sulfide ions in the reaction solution is 1:2:

4.

4. According to the preparation method of claim 1, the molar ratio of nickel ions to iron ions in the electrolyte is 4:

1.

5. According to the preparation method of claim 1, the soaking solution contains 0.25M Na2S and 0.35M Na2SO3.

6. The preparation method according to claim 1, wherein the temperature of the solvothermal reaction is 150-170°C and the time is 5.5-6.5 hours.

7. The preparation method according to claim 1, wherein in the annealing treatment, the annealing temperature is 350℃~450℃ and the annealing time is 0.5~1.5 hours.

8. An electrode for photoelectrochemical sulfur oxidation, made by the method according to any one of claims 1-7.

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