WO2021027381A1

WO2021027381A1 - Preparation method for stannous tungstate film for achieving continuous photolysis of water

Info

Publication number: WO2021027381A1
Application number: PCT/CN2020/095418
Authority: WO
Inventors: 博热耶夫·法拉比; 阿金诺古·埃泽尔; 冯柯
Original assignee: 肇庆市华师大光电产业研究院
Priority date: 2019-08-12
Filing date: 2020-06-10
Publication date: 2021-02-18
Also published as: CN110295355A

Abstract

A preparation method for a stannous tungstate film for achieving continuous photolysis of water. The preparation method comprises: vacuumizing a reaction chamber by using a radio frequency reactive magnetron sputtering method until a vacuum degree of the reaction chamber reaches 4-6×10^-4 Pa; using a silicon wafer and FTO as a substrate; introducing argon gas; making reaction pressure at 1-3 Pa; preparing a stannous tungstate film by deposition and then performing nickel plating by using a magnetron sputtering method, the time of deposition for nickel plating being 20-30 min; and finally, performing vacuum annealing at 400-600°Ϲ for 20-30 min. According to the preparation method, a nickel protective layer is plated on the surface of a tin tungstate film, so that the film is stable and cracking of water is stable.

Description

Preparation method of stannous tungstate film for realizing continuous photolysis of water

This application claims the priority of a Chinese patent application filed with the Chinese Patent Office on August 12, 2019, the application number is 201910741354.4, and the invention title is "A method for preparing stannous tungstate film for continuous photolysis of water". The entire content is incorporated into this application by reference.

Technical field

The invention belongs to the technical field of stannous tungstate film preparation, and specifically relates to a method for preparing a stannous tungstate film for continuous photolysis of water.

Background technique

In recent years, the excessive use of fossil fuels has had an extremely serious impact on the climate, so it is necessary to vigorously develop renewable energy such as solar, wind, hydro, tidal and biomass energy. However, because renewable energy sources such as solar energy, wind energy, and tidal energy are extremely unstable, they need to be converted into electrical or chemical energy for storage. For example, it can be converted into hydrogen energy by electrolysis or photoelectrolysis of water. In order to make photoelectrolyzed water have good industrial application prospects, it is necessary to develop a large area of photoelectrode materials. A suitable photoelectrode material should have high solar energy conversion efficiency and long-term stability in the electrolyte. BiVO ₄ material has good characteristics of photoelectrolysis for hydrogen production, but its band gap is 2.5～2.7eV, water splitting energy is 1.23eV, so the effective way to improve photoelectrolysis of water is to use a bandwidth of 1.5～2eV material. α-SnWO ₄ material has suitable valence band and conduction band, and its bandwidth is close to the splitting energy of water. However, when it is used as an electrode, it has poor stability and cannot achieve continuous photolysis of water.

Summary of the invention

In order to overcome the above-mentioned shortcomings of the prior art, the present invention proposes a method for preparing a stannous tungstate film that realizes continuous photolysis of water. The invention is used to plate a nickel protective layer on a tin tungstate film, thereby achieving film stability.

The technical scheme adopted by the present invention is:

A preparation method of stannous tungstate film that realizes continuous photolysis of water. Using radio frequency reactive magnetron sputtering method, the reaction chamber is evacuated to make the vacuum degree reach 4～6×10 ^-4 Pa, silicon wafer and FTO Acting as a substrate, blow in argon gas, the reaction pressure is 1 ~ 3Pa, firstly prepare tin tungstate thin film, then nickel plating, the deposition time of the nickel plating is 20-30min, and finally vacuum annealing at 400-600℃ 20～30min.

Preferably, the reaction pressure is 3 Pa, the tin tungstate film is deposited and prepared first, and then nickel is plated by magnetron sputtering, and the deposition time of the nickel plating is 30 min.

Preferably, the nickel plating adopts electron beam deposition, magnetron sputtering or pulsed laser deposition.

More specifically, the present invention adopts the magnetron sputtering method to evacuate the reaction chamber to a vacuum degree of 6×10 ^-4 Pa. The silicon wafer and FTO serve as the substrate, and argon gas is introduced. The reaction pressure is 3 Pa. A thin film of tin tungstate was prepared by deposition, and then nickel-plated by magnetron sputtering. The deposition time was 30 minutes, and finally, it was annealed in vacuum at 600°C for 20 minutes.

In order to achieve a continuous photooxidation process, the thickness of the protective layer must be adjusted to maintain sufficient transparency while not absorbing a large amount of light. In order to achieve this thickness range, the deposition time of magnetron sputtering must be changed. Therefore, the present invention prepares nickel films stably for photohydrolysis through various deposition methods.

In addition, when the nickel protective layer is plated by reactive magnetron sputtering, the reaction conditions are highly controllable. When the pressure of the reaction chamber is controlled and the power applied to the target is the same, the composition and thickness of the resulting film are the same. A film with the same performance can be obtained.

Compared with the prior art, the beneficial effects of the present invention are:

In the present invention, a nickel protective layer is plated on the surface of the tin tungstate film, so that the split water reaction is stable, and the operation is simple, and it is easy to realize large-scale industrialization.

Description and drawings

Figure 1 is a schematic diagram of the film preparation process;

Figure 2 shows the preparation steps of Ni/SnWO ₄ film;

Figure 3 shows the relationship between the photocurrent density and time of the SnWO ₄ photoanode in 0.5MNa ₂ SO ₄ electrolyte under chopped AM1.5 illumination;

Figure 4 shows the XPS spectra of (a) Sn3d and (b) W4f of Ni-SnWO ₄ films prepared on FTO before and after the PEC test of 1.23V _RHE under 1h chopping AM1.5 irradiation;

Figure 5(a) is the linear sweep voltage (JV) curve of NiOx-SnWO ₄ photoanode on FTO substrate in 0.5MNa ₂ SO ₄ solution under chopping AM1.5 irradiation; (b) in chopping wave Under AM1.5 light, 1.83 and 2.23V _RHE , the photocurrent of NiO _x -SnWO ₄ photoanode changes with time;

FIG 6 is a chopping under irradiation AM1.5 1h, before and after the PEC 1.83V _RHE test, (a) Sn3d Ni-SnWO 4 film prepared on FTO XPS spectra and (b) W4f of;

detailed description

The specific embodiments and drawings of the present invention will be further described below. It should be noted here that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation to the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

Example 1

Firstly, the n-type silicon wafer and FTO were cleaned with propanol, absolute ethanol and deionized water in an ultrasonic cleaner for 10 minutes respectively, and then they were placed on the sample stage of the magnetron sputtering reaction chamber. Then, the reaction chamber was evacuated to a vacuum degree of 6×10 ^-4 Pa, as shown in Figure 1. Then, argon gas was introduced to make the pressure of the reaction chamber 3Pa.

Then, the tin tungstate tin film was prepared at room temperature by the radio frequency reactive magnetron sputtering method.

Next, a nickel film was plated on the surface of SnWO ₄ by radio frequency reactive magnetron sputtering. Under the same pressure (3Pa) and room temperature, the thickness of the nickel layer can be controlled by controlling the deposition time of nickel plating.

When the deposition time of nickel plating is 30 minutes, the thickness of the nickel layer is the best, which is 10 nm.

Finally, the Ni/SnWO ₄ sample was vacuum annealed in a muffle furnace at 600°C for 20 minutes. The preparation steps are shown in Figure 2.

Application experiment example

In a 0.5M Na ₂ SO ₄ solution, at 1.23V relative to a standard hydrogen electrode, a 300nm thick SnWO ₄ photoanode was subjected to a chopping light test for 1 hour (Figure 3). Experiments show that due to the large amount of Sn ²⁺ oxidized to the Sn ⁴⁺ state on the surface of the film, the photocurrent density drops rapidly from 0.27 mAcm ^-2 to 0.03 mAcm ^-2 . The XPS spectrum (Figure 4) shows that the original film shows Sn3d _3/2 and Sn3d _5/2 peaks at 486.4eV and 494.84eV, which are close to the literature values. After the PEC test, the two peaks moved to 486.97 eV and 495.44 eV, respectively, that is, due to the formation of the Sn ⁴⁺ oxidation state, the energy level of the two peaks increased. The tungsten peak also exhibits a similar behavior. Since the WO ₃ phase forms the SnWO ₄ phase, the tungsten peaks W4f _5/2 and W4f _7/2 move from 35ev and 35.73eV to 37.15eV and 37.88eV (Figure 4).

In order to improve the photoelectrochemical stability, the SnWO ₄ photoanode was plated with a nickel protective layer (the material prepared in Example 1) with a thickness of 10 nm using the radio frequency magnetron sputtering method. Under the dark/light condition of 0.5M Na ₂ SO ₄ electrolyte (pH=7), the linear scanning volt-rum curve of Ni-SnWO ₄ photoanode on FTO is shown in Fig. 5 a. In the first JV cycle, the dark current between 1.4 and 2V _RHE is oxidized by the nickel layer to form a NiO _x layer (

E=1.59V _RHE ). The tin tungstate film contains oxygen. When an electric potential and light are applied, the oxygen diffuses into the nickel film to form oxygen vacancies. After light exposure, electron holes are generated on the SnWO ₄ film, and the holes diffuse through the Ni film and are further oxidized. After the formation of the NiOx hole layer, water molecules are split by holes that reach the surface. Continuous Test 1 hour at 1.83V _RHE film photocurrent density stabilized at 0.16mA × cm ^-2, the current density at 2.23V _RHE time stable 0.75mA × cm ^-2 (Fig. 5 b). The photocurrent density value of b in Fig. 5 corresponds well to the potential value of a in Fig. 5. At 0～750s, the photocurrent density curve has a lot of noise. This is because O ₂ gas is generated on the surface of the photoelectrode, which affects the absorption of incident photons and the charge transfer at the semiconductor-electrolyte interface. Under 2.23V _RHE , after the film stably undergoes a 2h JV cycle, its photocurrent is slightly lower than the first JV cycle, but there is no dark current shoulder, which shows that the Ni film is not further oxidized (Figure 5). The XPS spectra of NiO _x -SnWO ₄ before and after the PEC test showed that after 1 hour of testing, the composition of the Sn3d and W4f peaks did not change significantly, indicating that the NiO _x layer can effectively protect the photoanode and make it work stably in solution (Figure 6).

In Figure 5, b is the stability test of the film in the solution at a potential of 1.83V _RHE . The experimental results show that after adding NiOx, the current density of the film after one hour of continuous operation in the solution hardly changes and is stable at 0.16mA×cm ^-2 indicates that the material has good photoelectric stability.

In the XPS spectrum of Figure 6, the components of the Sn3d and W4f peaks before and after the PEC test did not change significantly, which also shows that NiO _x can effectively improve the stability of SnWO ₄ .

The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, without departing from the principle and spirit of the present invention, various changes, modifications, substitutions and modifications to these embodiments still fall within the protection scope of the present invention.

Claims

A preparation method of stannous tungstate film for continuous photolysis of water, which is characterized in that a radio frequency reactive magnetron sputtering method is adopted to evacuate the reaction chamber, and argon gas is introduced. The reaction pressure is 1 to 3 Pa. The tin tungstate film is prepared by deposition, and then nickel is plated. The deposition time of the nickel plating is 20-30 minutes, and finally vacuum annealing is performed at 400-600° C. for 20-30 minutes.
The method for preparing the stannous tungstate film for continuous photolysis of water according to claim 1, wherein the nickel plating is deposited by electron beam deposition, magnetron sputtering or pulsed laser deposition.
The method for preparing a stannous tungstate film that realizes continuous photolysis of water according to claim 2, wherein the magnetron sputtering method is a radio frequency magnetron sputtering method.
The method for preparing stannous tungstate film for continuous photolysis of water according to claim 2, characterized in that the reaction pressure is 3 Pa, the tin tungstate film is prepared by first deposition, and then nickel is plated by magnetron sputtering. The deposition time of the nickel plating is 30 minutes.
The method for preparing a stannous tungstate film that realizes continuous photolysis of water according to claim 1, wherein the thickness of the nickel layer after nickel plating is 5-15 nm.
The method for preparing the stannous tungstate film for continuous photolysis of water according to claim 4, wherein the thickness of the nickel layer after nickel plating is 10 nm.
The method for preparing a stannous tungstate film that realizes continuous photolysis of water according to claim 1, wherein the silicon wafer and FTO serve as a substrate.
The method for preparing a stannous tungstate film for continuous photolysis of water according to claim 1, wherein the vacuum degree is 4-6×10 -4 Pa.
A stannous tungstate film prepared by the method for preparing a stannous tungstate film for continuous photolysis of water according to any one of claims 1 to 8.
The stannous tungstate thin film of claim 9 is used as a photoelectrode material in photolysis water.