CN113235124A

CN113235124A - S-FeOOH/bismuth vanadate composite photo-anode and preparation method thereof

Info

Publication number: CN113235124A
Application number: CN202110541825.4A
Authority: CN
Inventors: 卢小泉; 何耀荣; 张蓉芳; 贾元琪; 刘娟; 王妮; 阮晴; 焦小梅; 白蕾; 韩振刚
Original assignee: Northwest Normal University
Current assignee: Northwest Normal University
Priority date: 2021-05-18
Filing date: 2021-05-18
Publication date: 2021-08-10
Anticipated expiration: 2041-05-18
Also published as: CN113235124B

Abstract

The invention discloses an S-FeOOH/bismuth vanadate composite photo-anode and a preparation method thereof₄Thin film, then in BiVO₄FeOOH electrocatalyst is loaded on the film to obtain FeOOH/BiVO₄Film, finally FeOOH/BiVO₄Immersing the film into an ethanol solution of thioacetamide, reacting for 0.8-1 h at 80-100 ℃, cooling to room temperature, cleaning the film with ethanol, and drying in vacuum to obtain S-FeOOH/BiVO₄Is compounded withAnd a photo-anode. The invention successfully introduces nonmetal S element into the FeOOH/BiVO4 electrocatalyst, promotes the separation of electron holes on the interface, enhances the photoelectrochemical water decomposition efficiency, and enhances the stability of the composite material in the photoelectrochemical water oxidation process.

Description

S-FeOOH/bismuth vanadate composite photo-anode and preparation method thereof

Technical Field

The invention belongs to the technical field of photoelectrochemistry, and particularly relates to an S-FeOOH/bismuth vanadate composite photo-anode and a preparation method thereof.

Background

With the development of society and the demand for energy, there is an urgent need to shift from fossil energy systems to sustainable clean energy. Solar energy is a significant advance as the best candidate over existing fossil fuels, geothermal energy and wind energy. Photoelectrochemical water splitting (PEC) is the best strategy for efficient solar energy utilization. The most significant problem in the PEC process is the separation of carriers, with electrons and holes having severe recombination at the bulk and interface of the semiconductor. Scientists have found that coupling an electrocatalyst can further improve carrier separation efficiency, but still leaves some gap from theoretical values. It is therefore important to find new efficient electrocatalysts. In the invention, a nonmetallic element doping mode is adopted, thioacetamide is used as an S source, and FeOOH/BiVO is prepared by a solvothermal method₄The cocatalyst layer is subjected to in-situ S element doping to finally obtain S-FeOOH/BiVO₄The composite light anode.

Disclosure of Invention

The invention aims to provide an S-FeOOH/bismuth vanadate composite photo-anode and a preparation method thereof.

One, S-FeOOH/BiVO₄Preparation of composite photoelectrode

The preparation method of the S-FeOOH/bismuth vanadate composite photo-anode comprises the following steps:

(1) dissolving KI in ultrapure water, adding HNO₃Adjusting the pH value to 1.7-1.8, and adding Bi (NO)₃)₃·5H₂O, stirring for 10-30 min to form an electroplating solution, adding an absolute ethyl alcohol solution of p-benzoquinone into the electroplating solution, stirring and mixing uniformly, performing electrodeposition by adopting a three-electrode system, taking an FTO (fluorine-doped tin oxide) as a working electrode, an Ag/AgCl electrode as a reference electrode and a Pt sheet electrode as a counter electrode, and performing electrodeposition for 5-6 min under a potential of-0.1V relative to the Ag/AgCl electrode to obtain a BiOI electrode; immersing the BiOI electrode into a dimethyl sulfoxide solution of vanadyl acetylacetonate, heating the BiOI electrode to 450-500 ℃ in a muffle furnace at a heating rate of 2 ℃/min, maintaining the temperature for 2 hours, cooling the BiOI electrode to room temperature, and soaking the BiOI electrode in a NaOH solution to remove redundant V₂O₅Finally, rinsing with ultrapure water and drying in ambient air to obtain BiVO₄A film. Wherein KI and Bi (NO)₃)₃·5H₂The mass ratio of O is 2: 1-4: 1; the molar ratio of KI to p-benzoquinone is 1: 1-2: 1; the concentration of the absolute ethanol solution of the p-benzoquinone is 0.2-0.3M; the molar ratio of KI to vanadyl acetylacetonate is 1: 1-2: 1; the concentration of the vanadyl acetylacetonate in dimethyl sulfoxide was 0.2M.

(2) FeCl is added₃.6H₂Dissolving O in distilled water, adding NaNO₃Stirring to obtain mixed solution, and mixing the above BiVO₄Immersing the film in the mixed solution, reacting at 80-100 ℃ for 8-10 min, after the reaction is finished, thoroughly washing the film with distilled water, and finally drying to obtain FeOOH/BiVO₄A film. Wherein FeCl₃.6H₂O and NaNO₃The mass ratio of (A) to (B) is 1: 1-2: 1.

(3) The FeOOH/BiVO is added₄Immersing the film in an absolute ethanol solution of thioacetamide, reacting for 0.8-1 h at 80-100 ℃, cooling to room temperature, cleaning the film with ethanol, and drying in vacuum to obtain S-FeOOH/BiVO₄The composite light anode. Wherein the concentration of the anhydrous ethanol solution of thioacetamide is 40 mM-60 mM, and the vacuum drying is performed for 10-12 h at 50-60 ℃.

II, S-FeOOH/BiVO₄Characterization of composite photoelectrode

1、BiVO₄Characterization of the film

FIG. 1 is BiVO₄Ultraviolet-visible diffuse reflectance spectrum of the film. By making a tangent to the straight line portion of the graph intersecting the X-axis, it can be seen that the intersection is at 505nm, and BiVO is calculated by the formula Eg =1240/λ₄Has a band gap value of about 2.45 eV.

FIG. 2 is BiVO₄XRD pattern of the film. Confirming the peak position by comparing with a standard card, confirming the BiVO₄And (4) successfully preparing the film.

FIG. 3 is BiVO₄SEM image of the film, from which BiVO can be seen₄The film presents a worm-like appearance, and BiVO is also confirmed₄And (4) successfully preparing the film.

2. Characterization of FeOOH/BiVO4 film

FIG. 4 shows FeOOH/BiVO₄The SEM image shows that after FeOOH is deposited on the surface of BiVO4, a thin sheet-like structure is tightly covered on the BiVO₄On the film, successful loading of FeOOH catalyst was confirmed.

FIG. 5 shows FeOOH/BiVO₄The XRD pattern of the supported catalyst is not changed relative to the XRD pattern of BiVO4, which indicates that the supported catalyst does not act on BiVO₄The overall structure of (a) is destroyed and successful loading of the thin FeOOH layer is also confirmed.

3、S-FeOOH/BiVO₄Characterization of composite photoelectrode

FIG. 6 is an SEM image of the composite photo-electrode S-FeOOH/BiVO4, and it can be seen from the SEM image that after the introduction of non-metallic sulfur element, the morphology of the film is not damaged compared with that of the FeOOH/BiVO4 film, which confirms that the strategy of doping sulfur element by the solvothermal method adopted by the method is feasible.

FIG. 7 is an EDS map of the composite photoelectrode S-FeOOH/BiVO4 from which the successful incorporation of elemental sulfur into the composite material can be seen.

III, S-FeOOH/BiVO₄Photoelectric performance test of composite photoelectrode

FIG. 8 shows a composite photo-electrode S-FeOOH/BiVO₄The LSV test of (1) shows that pure BiVO can be seen₄Has a photocurrent value of 0.9mA/cm^-2，S-FeOOH/BiVO₄The light current value of the composite photo-anode reaches 2.4 mA/cm^-2. From this, it can be concluded that Fe doped with S element inhibits the recombination of electrons and holes, improving the PEC performance of the photoanode.

FIG. 9 shows a composite photo-electrode S-FeOOH/BiVO₄With FeOOH/BiVO₄The stability of (2) is tested, and S-FeOOH/BiVO can be seen from the figure₄The light current value of (2) is from 2.38 mA/cm within 2h^-2Reduced to 2.22mA/cm^-2And FeOOH/BiVO₄The light current value of (a) is from 1.63 mA/cm within 2h^-2Reduced to 0.96mA/cm^-2Therefore, the stability of the composite photoelectrode can be improved after the sulfur element is doped.

In summary, the present invention is in BiVO₄FeOOH electrocatalyst is loaded on the film to obtain FeOOH/BiVO₄Thin film, then using solvothermal method to make FeOOH/BiVO₄Non-metallic sulfur element is introduced into the surface of the film in situ to obtain a non-metallic element doped electrocatalyst/semiconductor material S-FeOOH/BiVO₄The composite light anode is simple, rapid and safe. The doping of the non-metal elements in the electrocatalyst can change the energy band bending between the electrocatalyst and a semiconductor interface, is beneficial to the effective separation of electrons and holes, increases the active sites on the surface, promotes the efficiency of photoelectrochemical water decomposition, enhances the stability of the composite material in the photoelectrochemical water decomposition process, can be well applied to the photoelectrochemical water decomposition process, and provides a new concept for the photoelectrochemical water decomposition process.

Drawings

FIG. 1 shows BiVO of the present invention₄A uv-vis diffuse reflectance spectrum of the film;

FIG. 2 shows BiVO of the present invention₄XRD pattern of the film;

FIG. 3 shows BiVO of the present invention₄SEM image of the film;

FIG. 4 shows FeOOH/BiVO of the present invention₄SEM picture of (1);

FIG. 5 shows FeOOH/BiVO of the present invention₄XRD pattern of the film;

FIG. 6 shows S-FeOOH/BiVO of the present invention₄SEM image of the composite photoelectrode;

FIG. 7 shows S-FeOOH/BiVO of the present invention₄EDS map of composite photoelectrode;

FIG. 8 shows S-FeOOH/BiVO of the present invention₄An LSV map of the composite photoelectrode;

FIG. 9 shows S-FeOOH/BiVO of the present invention₄And (3) a stability test chart of the composite photoelectrode.

Detailed Description

The following is a description of the S-FeOOH/BiVO of the present invention by way of specific embodiments₄The preparation method of the composite photoelectrode is further explained.

(1) Preparing BiVO on FTO substrate by adopting electrodeposition method₄A film. 20mmol of KI was dissolved in 50mL of ultrapure water and then purified by addition of HNO₃The pH was adjusted to 1.7. Subsequently, 0.97g of Bi (NO) was slowly added₃)₃·5H₂And O, stirring vigorously for 25min to form the electroplating solution. The plating solution was mixed with 20mL of absolute ethanol (100%) containing 0.23M p-benzoquinone. After stirring for 30 minutes, taking the FTO as a working electrode, the Ag/AgCl electrode as a reference electrode and the Pt sheet electrode as a counter electrode, and electrodepositing for 5 minutes under the potential of-0.1V (relative to Ag/AgCl) to prepare the BiOI electrode. The BiOI electrode was immersed in 0.2mL of a dimethyl sulfoxide solution containing 0.2M vanadyl acetylacetonate and heated in a muffle furnace at 450 ℃ for 2h (at a rate of 2 ℃ C. for min)⁻¹). In order to remove excess V₂O₅After cooling to room temperature, the photoanode was immersed in 1M NaOH solution for 30min and gently stirred. Finally, washing with ultrapure water, and drying in ambient air to obtain BiVO₄A film.

(2) Firstly 0.0810 g FeCl was weighed₃.6H₂O in a 100mL beaker, 30mL of distilled water was added to dissolve completely, and 0.0510 g of NaNO was added to the solution₃Stirring for 30min to form a mixed solution. BiVO (bismuth oxide) is added₄Immersing the film in the mixed solution, transferring the film into an 80mL autoclave containing a polytetrafluoroethylene lining, reacting for 10min at 100 ℃, thoroughly washing the film with distilled water after the reaction is finished, and finally drying the film to obtain the FeOOH/BiVO4 film.

(3) And doping elements by adopting a solvothermal method. Firstly weighing 0.0751g of thioacetamide to be dissolved in 20mL of absolute ethanol, immersing the FeOOH/BiVO4 film in the absolute ethanol of the thioacetamide and transferring the film into 80mL of autoclave containing polytetrafluoroethylene lining, reacting for 1h at 90 ℃, cooling to room temperature, then thoroughly cleaning the film with ethanol, and drying in vacuum for 12h at 60 ℃ to obtain S-FeOOH/BiVO₄And (4) a composite light anode. S-FeOOH/BiVO₄The light current value of the composite photo-anode is 2.4 mA/cm^-2。

Claims

1. A preparation method of an S-FeOOH/bismuth vanadate composite photo-anode comprises the following steps:

(1) dissolving KI in ultrapure water, adding HNO₃Adjusting the pH value to 1.7-1.8, and adding Bi (NO)₃)₃·5H₂O, stirring for 10-30 min to form an electroplating solution, adding an absolute ethyl alcohol solution of p-benzoquinone into the electroplating solution, stirring and mixing uniformly, performing electrodeposition by adopting a three-electrode system, taking an FTO (fluorine-doped tin oxide) as a working electrode, an Ag/AgCl electrode as a reference electrode and a Pt sheet electrode as a counter electrode, and performing electrodeposition for 5-6 min under a potential of-0.1V relative to the Ag/AgCl electrode to obtain a BiOI electrode; immersing the BiOI electrode into a dimethyl sulfoxide solution of vanadyl acetylacetonate, heating the BiOI electrode to 450-500 ℃ in a muffle furnace at a heating rate of 2 ℃/min, maintaining the temperature for 2 hours, cooling the BiOI electrode to room temperature, and soaking the BiOI electrode in a NaOH solution to remove redundant V₂O₅Finally, rinsing with ultrapure water and drying in ambient air to obtain BiVO₄A film;

(2) FeCl is added₃.6H₂Dissolving O in distilled water, adding NaNO₃Stirring to obtain mixed solution, and mixing the above BiVO₄Immersing the film in the mixed solution, reacting at 80-100 ℃ for 8-10 min, after the reaction is finished, thoroughly washing the film with distilled water, and finally drying to obtain FeOOH/BiVO₄A film;

(3) the FeOOH/BiVO is added₄Immersing the film in anhydrous ethanol solution of thioacetamide, reacting at 80-100 ℃ for 0.8-1 h, cooling to room temperature, washing the film with ethanol, vacuum drying,obtaining S-FeOOH/BiVO₄The composite light anode.

2. The method for preparing the S-FeOOH/bismuth vanadate composite photo-anode according to claim 1, which is characterized in that: in the step (1), KI and Bi (NO)₃)₃·5H₂The mass ratio of O is 2: 1-4: 1.

3. The method for preparing the S-FeOOH/bismuth vanadate composite photo-anode according to claim 1, which is characterized in that: in the step (1), the molar ratio of KI to p-benzoquinone is 1: 1-2: 1; the concentration of the absolute ethyl alcohol solution of the p-benzoquinone is 0.2-0.3M.

4. The method for preparing the S-FeOOH/bismuth vanadate composite photo-anode according to claim 1, which is characterized in that: in the step (1), the molar ratio of KI to vanadyl acetylacetonate is 1: 1-2: 1; the concentration of the vanadyl acetylacetonate in dimethyl sulfoxide was 0.2M.

5. The method for preparing the S-FeOOH/bismuth vanadate composite photo-anode according to claim 1, which is characterized in that: in step (2), FeCl₃.6H₂O and NaNO₃The mass ratio of (A) to (B) is 1: 1-2: 1.

6. The method for preparing the S-FeOOH/bismuth vanadate composite photo-anode according to claim 1, which is characterized in that: in the step (3), the concentration of the anhydrous ethanol solution of thioacetamide is 40 mM-60 mM.

7. The method for preparing the S-FeOOH/bismuth vanadate composite photo-anode according to claim 1, which is characterized in that: in the step (3), the vacuum drying is carried out for 10-12 hours at 50-60 ℃.

8. The S-FeOOH/bismuth vanadate composite photo-anode prepared by the method of any one of claims 1 to 7.