Titanium-doped bismuth vanadate thin film photoanode and preparation method thereof

Abstract

The application discloses a titanium-doped bismuth vanadate film photo-anode and a preparation method thereof. A precursor solution formed by mixing bismuth nitrate, an aqueous potassium iodide solution and an ethanol solution of benzoquinone is used as an electrolyte, fluorine-doped tin dioxide conductive glass (FTO) is used as a working electrode, a platinum sheet is used as a counter electrode, Ag / AgCl is used as a reference electrode, a bias voltage of -0.1 V vs. Ag / AgCl is applied to the working electrode, and a bismuth oxyiodide precursor film is deposited on the FTO. Then, a mixed solution of titanium tetrachloride and acetylacetone vanadyl dimethyl sulfoxide is added dropwise to the bismuth oxyiodide precursor film, and the titanium-doped bismuth vanadate film photo-anode is obtained through calcination and neutralization treatment. The titanium-doped bismuth vanadate film photo-anode has higher photoelectrocatalytic efficiency and charge transport efficiency, and can be widely applied to the fields of photoelectrocatalytic hydrogen production and photoelectrocatalytic degradation of pollutants.

Description

Technical Field

[0001] This invention relates to a technology in the field of photoelectrocatalysis, specifically a titanium-doped bismuth vanadate (Ti:BiVO4) thin-film photoanode and its preparation method. Background Technology

[0002] Bismuth vanadate (BiVO4) has advantages as a photoelectrocatalytic photoanode, including suitable conduction band / valence band positions (~2.4 eV), abundant reserves, low cost, non-toxicity, and good stability. However, BiVO4 has a relatively short hole diffusion length (~70 nm) and weak carrier mobility (~4.4 × 10⁻⁶). -2 cm -2 V -1 s -1 The limited use of BiVO4 in pollutant degradation and water decomposition has hindered its application. To overcome these drawbacks, introducing oxygen vacancies, constructing heterojunctions, and using doping elements can effectively accelerate the charge separation and transfer process in BiVO4 photoanodes. Existing technologies employ doping with P of the same valence state... 5+ Replaces V in BiVO4 5+ The position of the doped P-type carriers is adjusted to improve carrier mobility and lower the polaron transition energy barrier; however, doping with the same valence state of P-type carriers... 5+ Replace V 5+ This reduces oxygen vacancies in BiVO4, resulting in lower carrier density, which is detrimental to charge transfer and cannot effectively improve the photoelectrocatalytic performance of the electrode. Existing technologies use doping with high-valence metal ions (W). 6+ Or Mo 6+ Replaces V in BiVO4 5+ The position of the doping of BiVO4 can form a shallow electron donor level to improve the conductivity and carrier density of BiVO4 and enhance the photoelectrocatalytic performance of the BiVO4 thin film photoanode. However, high-valence metal ion doping is not conducive to the formation of oxygen vacancies in BiVO4, and excessively high doping concentration can lead to the generation of defect states, which become recombination centers of charge carriers, resulting in the inability to significantly improve the carrier density and the photoelectrochemical efficiency and charge transport efficiency of the photoanode. Summary of the Invention

[0003] To address the shortcomings of the prior art, this invention proposes a titanium-doped bismuth vanadate thin-film photoanode and its preparation method, using low-valence Ti... 4+ Replaces V in BiVO4 5+ A method for preparing titanium-doped bismuth vanadate (Ti:BiVO4) thin-film photoanodes was developed. The resulting Ti:BiVO4 thin-film photoanodes have abundant oxygen vacancies, generate high carrier density, and exhibit excellent charge transport efficiency and photoelectrocatalytic performance. They can be widely used in photoelectrocatalytic degradation of pollutants and water decomposition for hydrogen production.

[0004] This invention is achieved through the following technical solution:

[0005] This invention relates to a titanium-doped bismuth vanadate thin-film photoanode and its preparation method. The method uses a precursor solution composed of bismuth nitrate, potassium iodide aqueous solution, and p-benzoquinone ethanol solution as the electrolyte; fluorine-doped tin oxide conductive glass (FTO) as the working electrode; a platinum sheet as the counter electrode; and Ag / AgCl as the reference electrode. A bias voltage of -0.1V vs. Ag / AgCl is applied to the working electrode, and a bismuth oxyiodide precursor film is deposited on the FTO. Then, a mixed solution of titanium tetrachloride and vanadium acetylacetonate dimethyl sulfoxide is dropped onto the bismuth oxyiodide precursor film, and the titanium-doped bismuth vanadate thin-film photoanode is obtained through calcination and neutralization.

[0006] The deposition time is 300-500 seconds.

[0007] The dimethyl sulfoxide mixed solution contains 0.1–0.4 mM titanium tetrachloride and 0.2 M vanadium acetylacetonate.

[0008] The calcination is carried out at 350–550°C for 2 hours.

[0009] The neutralization treatment involves, but is not limited to, soaking in a 1M sodium hydroxide solution for 30 minutes to remove excess V2O5 from the surface, followed by rinsing several times with deionized water and drying.

[0010] The preferred aqueous solution of bismuth nitrate and potassium iodide is a 0.04M bismuth nitrate and 0.4M potassium iodide aqueous solution with a pH of 1.6 to 1.8.

[0011] The preferred ethanol solution of p-benzoquinone is a 0.23M ethanol solution of p-benzoquinone.

[0012] The ratio of the aqueous solution of bismuth nitrate and potassium iodide to the ethanol solution of p-benzoquinone is 5:2.

[0013] Technical effect

[0014] Compared with the prior art, the present invention utilizes low-valence Ti 4+ Replaces V in BiVO4 5+ The formation of abundant oxygen vacancies in BiVO4 significantly increases the charge carrier density and photocurrent of the photoanode, reduces the interfacial transport resistance of the photoanode, and solves the problems of weak charge separation and transfer ability and low oxygen vacancy concentration of the bismuth vanadate film photoanode. The photoelectrocatalytic performance of the prepared Ti:BiVO4 is greatly improved. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the Ti:BiVO4 preparation process of the present invention;

[0016] Figure 2The Ti:BiVO4 thin-film photoanode of Example 1 and the BiVO4 thin-film photoanode of Control Example 1 were compared in a 0.2M Na2SO4 electrolyte at 100mW cm⁻¹ -2 A schematic diagram of the linear scanning voltammetry curve measured under illumination intensity;

[0017] Figure 3 The Ti:BiVO4 thin-film photoanode of Example 1 and the BiVO4 thin-film photoanode of Control Example 1 were compared in a 0.2M Na2SO4 electrolyte at 100mW cm⁻¹ -2 A schematic diagram of the photoelectric conversion efficiency curves measured under light intensity and a bias voltage of 1.23V vs. RHE;

[0018] Figure 4 This is a schematic diagram of the Mott-Schottky curves of the Ti:BiVO4 thin film photoanode of Example 1 and the BiVO4 thin film photoanode of Control Example 1.

[0019] Figure 5 This is a schematic diagram of the AC impedance curves of the Ti:BiVO4 thin film photoanode of Example 1 and the BiVO4 thin film photoanode of Control Example 1.

[0020] Figure 6 X-ray photoelectron spectra of the Ti:BiVO4 thin film photoanode of Example 1 and the BiVO4 thin film photoanode of Comparative Example 1. Detailed Implementation

[0021] Example 1

[0022] This embodiment relates to a method for preparing a Ti:BiVO4 thin-film photoanode, specifically including: using a precursor solution as the electrolyte, fluorine-doped tin oxide conductive glass (FTO) as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, applying a bias voltage of -0.1V vs. Ag / AgCl to the working electrode, depositing a bismuth oxyiodide precursor film on the FTO for 400 seconds; subsequently, dropping a mixed solution of dimethyl sulfoxide containing 0.2mM titanium tetrachloride and 0.2M vanadium acetylacetonate onto the bismuth oxyiodide surface, and calcining at 450°C for 2 hours; then immersing the sintered sample in a 1M sodium hydroxide solution for 30 minutes to remove excess V2O5 from the surface, rinsing it several times with deionized water and drying it to obtain the Ti:BiVO4 thin-film photoanode.

[0023] The precursor solution described in this embodiment is composed of 50 mL of a pH 1.7 aqueous solution of 0.04 M bismuth nitrate and 0.4 M potassium iodide and 20 mL of a 0.23 M p-benzoquinone ethanol solution.

[0024] The Ti:BiVO4 thin-film photoanode prepared in this embodiment was placed in a 0.2M Na2SO4 electrolyte solution at a 100mW / cm² temperature. -2 LSV curves under illumination intensity are as follows Figure 2 As shown, its photocurrent density is 2.51 mA / cm² at a bias voltage of 1.23 V vs. RHE. -2 ;like Figure 3 As shown, Ti:BiVO4 has a photoelectric conversion efficiency as high as 28.4%.

[0025] like Figure 4 As shown, the Ti:BiVO4 thin-film photoanode has a charge carrier density of 5.86 × 10⁻⁶. 18 cm -3 .

[0026] like Figure 5 As shown, the interface transfer resistance of Ti:BiVO4 is 399.5Ω.

[0027] like Figure 6 As shown, X-ray photoelectron spectroscopy confirmed the formation of a very distinct oxygen vacancy peak in Ti:BiVO4, with a peak integral area of ​​approximately 9692. This thin-film photoanode can be used as a photoelectrocatalytic electrode for photoelectrocatalytic hydrogen production and photoelectrocatalytic degradation of pollutants.

[0028] Compare with Examples 1-4

[0029] The comparative example relates to a method for preparing an undoped Ti-based BiVO4 thin-film photoanode, specifically including: using a precursor solution as the electrolyte, FTO as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, applying a bias voltage of -0.1V vs. Ag / AgCl to the working electrode, depositing a bismuth oxyiodide precursor film on the FTO for 400 seconds; subsequently, dropping a 0.2M solution of vanadium acetylacetonate dimethyl sulfoxide onto the bismuth oxyiodide surface, and calcining at 450°C for 2 hours; then immersing the sintered sample in a 1M sodium hydroxide solution for 30 minutes to remove excess V2O5 from the surface, rinsing it several times with deionized water and drying it to obtain the BiVO4 thin-film photoanode.

[0030] The precursor solution described in the comparative example was composed of 50 mL of a pH 1.7 aqueous solution of 0.04 M bismuth nitrate and 0.4 M potassium iodide and 20 mL of an ethanolic solution of 0.23 M p-benzoquinone.

[0031] The BiVO4 thin-film photoanode prepared in the comparative example was placed in a 0.2 M Na2SO4 electrolyte solution at 100 mW cm⁻¹. -2 Electrochemical tests under illumination showed that its photocurrent density was 1.32 mA / cm² at a bias voltage of 1.23 V vs. RHE.-2 The photoelectric conversion efficiency was only 8.3% (28.4% in Example 1); the interfacial transport resistance of the BiVO4 thin-film photoanode was 1048.0Ω (399.5Ω in Example 1); such as Figure 6 As shown, X-ray photoelectron spectroscopy determined that the integrated area of ​​the oxygen vacancy peak in the BiVO4 thin film of Comparative Example 1 was significantly smaller, at 7806 (9692 in Example 1).

[0032] Table 1 lists the literature (comparative examples 2-4) on P-doped with the same valence state. 5+ Replaces V in BiVO4 5+ The formed photoelectrode material (P:BiVO4) is doped with high-valence metal ions W 6+ Or Mo 6+ Replaces V in BiVO4 5+ The reported charge carrier density data for the formed photoelectrode materials (W:BiVO4, Mo:BiVO4) are shown in Table 1. As can be seen from Table 1, the charge carrier density of the Ti:BiVO4 thin-film photoanode in Example 1 is 5.86 × 10⁻⁶. 18 cm -3 The values ​​were 3.13 times that of P:BiVO4 (Comparative Example 2), 3.42 times that of W:BiVO4 (Comparative Example 3), and 5.23 times that of Mo:BiVO4 (Comparative Example 4), respectively.

[0033] Table 1 Comparison of charge carrier density between Comparative Examples 2-4 and Example 1

[0034]

[0035] Example 2

[0036] This embodiment relates to a method for preparing a titanium Ti:BiVO4 thin film photoanode, specifically including: using a precursor solution as the electrolyte, using FTO as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, applying a bias voltage of -0.1V vs. Ag / AgCl to the working electrode, depositing a bismuth oxyiodide precursor film on the FTO for 300 seconds; subsequently, dropping a mixed solution of dimethyl sulfoxide containing 0.1mM titanium tetrachloride and 0.2M vanadium acetylacetonate onto the bismuth oxyiodide surface, and calcining at 350°C for 2 hours; then immersing the sintered sample in a 1M sodium hydroxide solution for 30 minutes to remove excess V2O5 from the surface, rinsing it several times with deionized water and drying it to obtain the Ti:BiVO4 thin film photoanode.

[0037] The precursor solution described in this embodiment is composed of 50 mL of a pH 1.6 aqueous solution of 0.04 M bismuth nitrate and 0.4 M potassium iodide and 20 mL of a 0.23 M p-benzoquinone ethanol solution.

[0038] The Ti:BiVO4 thin-film photoanode prepared in this embodiment was used in a 0.2M Na2SO4 electrolyte solution at 100mW / cm². -2 Electrochemical tests under illumination showed that its photocurrent density was 1.89 mA / cm² at a bias voltage of 1.23 V vs. RHE. -2 This thin-film photoanode can be used as a photoelectrocatalytic electrode for photoelectrocatalytic hydrogen production and photoelectrocatalytic degradation of pollutants.

[0039] Example 3

[0040] This embodiment relates to a method for preparing a Ti:BiVO4 thin-film photoanode, specifically including: using a precursor solution as the electrolyte, FTO as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, applying a bias voltage of -0.1V vs. Ag / AgCl to the working electrode, depositing a bismuth oxyiodide precursor film on the FTO for 500 seconds; subsequently, dropping a mixed solution of dimethyl sulfoxide containing 0.4mM titanium tetrachloride and 0.2M vanadium acetylacetonate onto the bismuth oxyiodide surface, and calcining at 550°C for 2 hours; then immersing the sintered sample in a 1M sodium hydroxide solution for 30 minutes to remove excess V2O5 from the surface, rinsing it several times with deionized water and drying it to obtain the Ti:BiVO4 thin-film photoanode.

[0041] The precursor solution described in this embodiment is composed of 50 mL of a pH 1.8 aqueous solution of 0.04 M bismuth nitrate and 0.4 M potassium iodide and 20 mL of a 0.23 M p-benzoquinone ethanol solution.

[0042] The Ti:BiVO4 thin-film photoanode prepared in this embodiment was used in a 0.2M Na2SO4 electrolyte solution at 100mW / cm². -2 Electrochemical tests under illumination showed that its photocurrent density was 2.23 mA / cm² at a bias voltage of 1.23 V vs. RHE. -2 This thin-film photoanode can be used as a photoelectrocatalytic electrode for photoelectrocatalytic hydrogen production and photoelectrocatalytic degradation of pollutants.

[0043] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A method for preparing a titanium-doped bismuth vanadate thin film photoanode, characterized in that, A precursor solution consisting of bismuth nitrate, potassium iodide aqueous solution, and p-benzoquinone ethanol solution was used as the electrolyte. Fluorine-doped tin oxide conductive glass (FTO) was used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode. A bias voltage of -0.1 V vs. Ag / AgCl was applied to the working electrode to deposit a bismuth iodide oxynitrate precursor film on the FTO. Then, a mixed solution of titanium tetrachloride and vanadium acetylacetonate dimethyl sulfoxide was dropped onto the bismuth iodide oxynitrate precursor film, and titanium-doped bismuth vanadate thin film photoanode was obtained by calcination and neutralization treatment.

2. The method of claim 1, wherein the method further comprises the step of: The deposition time is 300-500 seconds.

3. The method of claim 1, wherein the method further comprises the step of: The dimethyl sulfoxide mixed solution contains 0.1~0.4 mM titanium tetrachloride and 0.2 M vanadium acetylacetonate. ​ 4. The method of claim 1, wherein the method further comprises the step of: The calcination is carried out at 350~550 ℃ for 2 hours.

5. The method of claim 1, wherein the method further comprises the step of: The neutralization treatment involves soaking the sample in a 1 M sodium hydroxide solution for 30 minutes to remove excess V2O5 from the surface. After removal, the sample is rinsed several times with deionized water and then dried. ​ 6. The method of claim 1, wherein the method further comprises the step of: The bismuth nitrate and potassium iodide aqueous solution is a 0.04 M bismuth nitrate and 0.4 M potassium iodide aqueous solution with a pH of 1.6~1.8; The ethanol solution of p-benzoquinone is a 0.23M ethanol solution of p-benzoquinone.

7. The method according to claim 6, wherein the method is characterized by, The ratio of the aqueous solution of bismuth nitrate and potassium iodide to the ethanol solution of p-benzoquinone is 5:2.

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