A broad-spectrum response type BiVO4-based photocatalytic electrode and a preparation method and application thereof

Abstract

The application discloses a wide-spectrum-response BiVO4-based photocatalytic electrode and a preparation method and application thereof, and belongs to the technical field of photocatalytic electrodes, and comprises a conductive substrate and a photocatalyst loaded on the surface of the conductive substrate, wherein the photocatalyst is composed of BiVO4, a narrow-band-gap semiconductor material and a cocatalyst; and the specific preparation steps are as follows: S1, preparing BiVO4 on the surface of the conductive substrate to obtain a BiVO4 electrode; S2, immersing the BiVO4 electrode into a Co salt solution, and applying a potential to make Co ions adsorbed on the surface of the BiVO4 electrode; S3, immersing the BiVO4 electrode with the adsorbed Co ions into a Na2S solution, and then washing and drying to obtain a wide-spectrum-response photocatalytic electrode. The narrow-band-gap semiconductor material Bi2S3 and the cocatalyst CoS are prepared in situ on the surface of BiVO4 by an ion exchange method x , which can effectively widen the light absorption range of the BiVO4-based photocatalytic material, and improve the photoelectric response signal of the BiVO4-based photocatalytic electrode under visible and near-infrared light excitation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photocatalytic electrodes, in particular to a wide-spectrum response type BiVO4-based photocatalytic electrode and a preparation method and application thereof. BACKGROUND

[0002] The self-powered photoelectrochemical sensing method based on the development of photocatalytic fuel cells has the advantages of low cost, no need for external power supply, easy miniaturization, etc., and has emerged in the field of biological analysis. In order to avoid damage to biomolecules in such a sensing system by high-energy photons, long-wave visible light or near-infrared light with good biocompatibility is often used as an excitation light source to construct a sensing system. Bismuth vanadate (BiVO4) is widely used in photocatalytic related fields due to its good optical properties, high carrier mobility and excellent anti-photocorrosion stability. However, the large band gap width (~2.5eV) of bismuth vanadate makes it only be excited by visible light with a wavelength less than 520nm, and it cannot effectively utilize the long-wave visible light and near-infrared light with a high proportion in sunlight and good biocompatibility.

[0003] Therefore, a wide-spectrum response type BiVO4-based photocatalytic electrode is proposed, which can not only improve the utilization efficiency of sunlight, but also promote its application in photoelectrochemical biosensors. SUMMARY

[0004] The purpose of the present application is to provide a wide-spectrum response type BiVO4-based photocatalytic electrode and a preparation method and application thereof, in order to solve the problems in the background art.

[0005] To achieve the above-mentioned purpose, the present application provides a wide-spectrum response type BiVO4-based photocatalytic electrode, comprising a conductive substrate and a photocatalyst loaded on the surface of the conductive substrate, the photocatalyst being composed of BiVO4, a narrow-band-gap semiconductor material and a cocatalyst,

[0006] Preferably, the narrow-band-gap semiconductor material is Bi2S3, and the cocatalyst is CoS x .

[0007] Preferably, the conductive substrate is a conductive glass electrode, a glassy carbon electrode, a graphite electrode or a titanium electrode.

[0008] The present application also provides a preparation method of a wide-spectrum response type BiVO4-based photocatalytic electrode, comprising the following steps:

[0009] S1, preparing BiVO4 on the surface of a conductive substrate to obtain a BiVO4 electrode;

[0010] S2, immersing the BiVO4 electrode in a Co salt solution and applying a potential to make Co ions adsorbed on the surface of the BiVO4 electrode;

[0011] S3, immersing the BiVO4 electrode adsorbed with Co ions into a Na2S solution, rinsing and drying to obtain a light catalytic electrode with wide spectrum response.

[0012] Preferably, the specific steps of S1 are:

[0013] S11, electrodepositing a BiOI thin film on a conductive substrate;

[0014] S12, converting the BiOI into BiVO4 at high temperature with vanadyl acetylacetonate as a vanadium source.

[0015] Preferably, the specific steps of S11 are:

[0016] 1) adding a bismuth salt solution into a solution containing KI, adjusting pH and adding an ethanol solution of p-benzoquinone, and stirring to obtain an electrolyte;

[0017] 2) ultrasonic cleaning the conductive substrate; then using the conductive substrate after ultrasonic cleaning as a working electrode, using a saturated calomel electrode as a reference electrode and a platinum sheet as a counter electrode, and electrodepositing a BiOI thin film by using a three-electrode system.

[0018] Preferably, the specific steps of S12 are:

[0019] drying the electrodeposited BiOI thin film, dropping vanadyl acetylacetonate dimethyl sulfoxide solution on the surface of the BiOI thin film after cooling, calcining in a muffle furnace, immersing in a NaOH solution after cooling to room temperature, rinsing with pure water and drying in air to obtain a BiVO4 anode.

[0020] Preferably, in S12, the drying temperature is 80-120 DEG C, the time is 30-45 min, the calcining temperature is 400-500 DEG C, and the calcining time is 1.5-3 h.

[0021] Preferably, in S2, the concentration of Co salt is 1 mmol / L -1 -10 mmol / L -1 , the Co salt is one of cobalt nitrate, cobalt acetate or cobalt chloride; and the applied potential is 1-2 V.

[0022] The wide spectrum response BiVO4-based light catalytic electrode is applied to a self-powered photoelectrochemical sensor induced by near-infrared light.

[0023] Therefore, the wide spectrum response BiVO4-based light catalytic electrode, the preparation method and the application thereof have the advantages that a narrow-band semiconductor Bi2S3 and a cocatalyst CoS are prepared in situ on the surface of BiVO4 through ion exchange, the prepared electrode has a wide spectrum response, the electrode has a high photoelectric conversion efficiency, and the electrode has a high stability. xThe problem that BiVO4 is not easy to be excited by long-wavelength visible light and near-infrared light is solved, and the photoelectrocatalytic performance of the BiVO4 electrode is improved.

[0024] Specifically, bismuth sulfide is selected as a narrow-band-gap semiconductor in the photocatalyst, the bismuth sulfide has a wide light absorption range, and a wide-spectrum response type photocatalytic material with a matching energy level structure can be formed after the bismuth sulfide is coupled with the bismuth vanadate; the photo-generated electrons generated after the photocatalytic material is excited can be spontaneously transferred from the bismuth sulfide to the bismuth vanadate, and the holes are transferred from the bismuth vanadate with a lower valence band energy level to the bismuth sulfide, so that the recombination of the electron-hole pairs is significantly inhibited.

[0025] The CoS x The loading of the CoS x assist catalyst can improve the photocurrent of the photocatalytic electrode by reducing the activation energy of the oxygen evolution reaction, and further improve the photoelectrochemical response of the composite electrode under wide spectrum; in the method of the application, the narrow-band-gap semiconductor material Bi2S3 and the CoS x assist catalyst are prepared in situ on the surface of the BiVO4 by an ion exchange method, so that the wide-spectrum response type BiVO4-based photocatalytic electrode is constructed.

[0026] In addition, the wide-spectrum response type electrode prepared in the application is applied to a self-powered photoelectrochemical biosensor initiated by near-infrared light, and the near-infrared light has the advantages of small bleaching and low biological toxicity, which is conducive to improving the sensitivity and practicability of the sensing method.

[0027] The technical solutions of the application will be further described in detail below with reference to the drawings and examples. DESCRIPTION OF DRAWINGS

[0028] Figure 1 The microstructure diagram of the photoelectrode prepared in the examples and the comparative examples of the application is shown, wherein a is the example, and b is the comparative example;

[0029] Figure 2 The UV-Vis-NIR diffuse reflectance spectrum of the photoelectrode prepared in the examples and the comparative examples of the application is shown, wherein a is the example, and b is the comparative example;

[0030] Figure 3 The photocurrent response diagram of the photoelectrode prepared in the examples and the comparative examples of the application under visible light (405 nm) band illumination is shown;

[0031] Figure 4 The photocurrent response diagram of the photoelectrode prepared in the examples and the comparative examples of the application under near-infrared light (808 nm) band illumination is shown;

[0032] Figure 5 The schematic diagram of the photocatalytic cell in the application example of the application is shown;

[0033] Figure 6The response graph and linear fitting graph of a self-powered photoelectrochemical sensor based on the photocatalytic electrode prepared in the embodiment for application of the present application to different concentrations of target substances, wherein a is the response graph to different concentrations of target substances, and b is the linear fitting graph. DETAILED DESCRIPTION

[0034] The technical solutions of the present application are further described below by means of the accompanying drawings and embodiments.

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments.

[0036] EMBODIMENT

[0037] A BiVO4-based photocatalytic electrode with wide spectral response was prepared, using fluorine-doped tin oxide (FTO) conductive glass as a conductive substrate, BiVO4, Bi2S3, CoS x The specific steps are as follows:

[0038] S1, preparing BiVO4 on the surface of the conductive substrate to obtain a BiVO4 electrode, specifically:

[0039] 1) 0.97g of Bi(NO3)3·5H2O was added to 50mL of a solution containing 3.32g of KI (previously adjusted to pH 1.7±0.1), followed by 20mL of an ethanol solution containing 0.49g of p-benzoquinone, and the mixture was stirred to obtain an electrolyte;

[0040] 2) The fluorine-doped tin oxide (FTO) conductive glass was cut into small pieces of 2cm×2.5cm, and was ultrasonically cleaned in ethanol and saturated potassium carbonate methanol solution for 20 minutes respectively, and was then dried with nitrogen. The cleaned FTO was used as the working electrode, the saturated calomel electrode was used as the reference electrode, and the platinum plate was used as the counter electrode. A three-electrode system was used to electrodeposited at-0.1V (vs SCE) for 300s to obtain a uniform BiOI thin film electrode.

[0041] 3) The BiOI thin film electrode was dried at 100℃ for 30 minutes, and after cooling, 200μL of 0.2M vanadyl acetylacetonate dimethyl sulfoxide solution was dropped on the surface and calcined in a muffle furnace at a temperature increasing rate of 2℃ / min to 450℃ for 2h; after cooling to room temperature, the electrode was immersed in 1M NaOH solution and slowly shaken to remove excess V2O5. After washing with pure water, it was dried in air to obtain a BiVO4 photoanode.

[0042] S2, immerse the BiVO4 electrode into a Co salt solution, and apply a potential to make Co ions adsorbed on the surface of the BiVO4 electrode, specifically:

[0043] 80 mg of cobalt acetate tetrahydrate is dissolved in 120 mL of deionized water to form an electrolyte containing Co ions. A three-electrode system is built with the BiVO4 electrode, a saturated calomel electrode, and a platinum sheet as the working electrode, the reference electrode, and the counter electrode, respectively. Co ions are adsorbed on the surface of the BiVO4 electrode by the electric field effect under a voltage of 2 V for 20 minutes.

[0044] S3, immerse the BiVO4 electrode adsorbed with Co ions into a 0.03 M Na2S solution for 10 minutes, and generate CoS on the surface by in-situ ion exchange reaction between Co ions, BiVO4 and Na2S x -Bi2S3, to obtain a wide-spectrum response type BiVO4-based photocatalytic electrode.

[0045] Comparative Example

[0046] In this comparative example, fluorine-doped tin oxide (FTO) conductive glass is used as the conductive substrate, and BiVO4 is used as the photocatalyst. The specific steps are the same as in the examples, except that the steps involving Bi2S3, CoS x are removed.

[0047] The products prepared in the examples and the comparative example are analyzed and tested, and the microstructure diagram is shown in Figure 1 . The photocatalyst electrodes prepared in the examples and the comparative example are characterized by ultraviolet-visible-near infrared diffuse reflectance spectroscopy, and the results are shown in Figure 2 .

[0048] From the ultraviolet-visible-near infrared diffuse reflectance spectroscopy, it can be seen that the in-situ modification of CoS x -Bi2S3 on the surface of the BiVO4 photoelectrode can significantly improve the absorption of visible light and near-infrared light by the BiVO4 photoelectrode, and therefore the photoelectrochemical system based on the modified electrode can improve the utilization efficiency of solar spectrum.

[0049] The photocatalytic electrodes prepared in the examples and the comparative example are tested for photocurrent, and the test process uses the photocatalytic electrode as the working electrode, the saturated calomel electrode as the reference electrode, and the Pt wire electrode as the counter electrode to form a three-electrode system, and the results are shown in Figure 3 , 4 . It can be seen that under visible light (405 nm) or near-infrared light (808 nm) excitation, CoS xBi2S3 can significantly improve the photoelectric signal of the BiVO4 electrode, which is mainly due to the narrow band gap semiconductor bismuth sulfide which enhances the light absorption and promotes the migration of BiVO4 photo-generated carriers, and the cocatalyst CoS x Catalytic effect on water oxidation reaction.

[0050] The photocatalyst electrode prepared in the examples is applied to a near-infrared light-induced self-powered photoelectrochemical sensor, as follows:

[0051] Application examples

[0052] As Figure 5 shown, the prepared CoS x The Bi2S3 / BiVO4 photocatalytic electrode is used as a photoanode, a Prussian blue modified electrode is used as a cathode, and a quartz reaction cell containing K2SO4 solution is inserted, and is connected through an external circuit, to assemble a single-chamber photocatalytic cell.

[0053] The photoanode is irradiated with an 808 nm near-infrared light source, and the photoanode is excited to produce effective electron-hole pair separation and form a current path with the cathode, thereby generating electrical energy, and the output performance of the cell is recorded and analyzed by an electrochemical workstation. The surface of the photoanode is modified with an aptamer that can specifically recognize the target analyte ethinyl estradiol as a recognition element, and the determination of ethinyl estradiol is realized by the decrease in the output performance of the cell caused by the capture of the target analyte by the aptamer. The response graph of the self-powered photoelectrochemical sensor to different concentrations of target substances and the linear fitting graph are shown in Figure 6 , which shows the output performance of the photoanode constructed photocatalytic cell capturing different concentrations of ethinyl estradiol; the maximum output power of the photocatalytic cell has a good linear relationship with the logarithmic value of the concentration of ethinyl estradiol, thereby realizing the near-infrared induced self-powered photoelectrochemical detection of ethinyl estradiol.

[0054] Therefore, the present application is a wide-spectrum response type BiVO4-based photocatalytic electrode and its preparation method and application, which realizes the construction of a wide-spectrum response type BiVO4-based photocatalytic electrode by in-situ preparation of a narrow-band semiconductor material Bi2S3 and a cocatalyst CoS x on the surface of BiVO4 by ion exchange; and applies it to a near-infrared light-induced self-powered photoelectrochemical biosensor, which takes advantage of the low near-infrared light bleaching and low biological toxicity, and is beneficial to improve the sensitivity and practicability of the sensing method.

[0055] It should be pointed out finally that the above examples are only used to illustrate the technical solutions of the present application but not to limit it, and although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can still be modified or replaced equivalently, and these modifications or equivalent replacements should not make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A broadband responsive BiVO4-based photocatalytic electrode, characterized in that: The system includes a conductive substrate and a photocatalyst supported on the surface of the conductive substrate. The photocatalyst is composed of BiVO4, a narrow bandgap semiconductor material, and a cocatalyst. The narrow bandgap semiconductor material is Bi2S3, and the cocatalyst is CoS. x ; The above-mentioned method for preparing a broadband responsive BiVO4-based photocatalytic electrode involves in-situ preparation of a narrow bandgap semiconductor Bi2S3 and a co-catalyst CoS on the BiVO4 surface via ion exchange. x The steps are as follows: S1. Prepare BiVO4 on the surface of a conductive substrate to obtain a BiVO4 electrode; the specific steps are as follows: S11. Electrodeposit a BiOI thin film on a conductive substrate; The specific steps are as follows: 1) Add the bismuth salt solution to the solution containing KI, adjust the pH, add the ethanol solution of p-benzoquinone, stir and mix well to obtain the electrolyte; 2) Perform ultrasonic cleaning on the conductive substrate; Then, the ultrasonically treated conductive substrate was used as the working electrode, a saturated calomel electrode was used as the reference electrode, and a platinum sheet was used as the counter electrode to electrodeposit a BiOI thin film using a three-electrode system. S12. Using vanadium acetylacetonate as the vanadium source, BiOI is converted to BiVO4 at high temperature; S2. Immerse the BiVO4 electrode in a Co salt solution and apply a potential to cause Co ions to adsorb onto the surface of the BiVO4 electrode. S3. Immerse the BiVO4 electrode with adsorbed Co ions into Na2S solution, rinse and dry to obtain a broadband responsive photocatalytic electrode. A broadband responsive BiVO4-based photocatalytic electrode was applied to a near-infrared light-induced self-powered photoelectrochemical sensor. The prepared photocatalytic electrode was used as the photoanode, and the Prussian blue modified electrode was used as the cathode. The electrode was inserted into a quartz reaction cell containing K2SO4 solution and connected through an external circuit to assemble a single-chamber photocatalytic cell. When a near-infrared light source is used to irradiate a photoanode, the photoanode is excited to generate effective electron-hole pair separation and form a current path with the cathode, thereby generating electrical energy.

2. The broadband responsive BiVO4-based photocatalytic electrode according to claim 1, characterized in that: The conductive substrate is a conductive glass electrode, a glassy carbon electrode, a graphite electrode, or a titanium electrode.

3. The broadband responsive BiVO4-based photocatalytic electrode according to claim 1, characterized in that, The specific steps of S12 are as follows: The electrodeposited BiOI film was dried and cooled. A dimethyl sulfoxide solution of vanadium acetylacetonate was then drop-coated onto the surface of the BiOI film. The film was then calcined in a muffle furnace. After cooling to room temperature, the film was immersed in NaOH solution, rinsed with pure water, and dried in air to obtain the BiVO4 anode.

4. The broadband responsive BiVO4-based photocatalytic electrode according to claim 3, characterized in that: In S12, the drying temperature is 80-120℃, the time is 30-45 min, the calcination temperature is 400-500℃, and the calcination time is 1.5-3 h.

5. The broadband responsive BiVO4-based photocatalytic electrode according to claim 1, characterized in that: In S2, the concentration of Co salt is 1 mmol / L. -1 ~10 mmol / L -1 The Co salt is one of cobalt nitrate, cobalt acetate, or cobalt chloride; the applied potential is 1V to 2V.

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