Bismuth Tungstate Thin Film Preparation Method

The excessive use of fossil fuels has caused global temperatures to continue to rise, and the search for new clean energy is becoming imminent. Among the existing emerging energy sources, solar energy has received much attention as an inexhaustible and pollution-free energy source.

Since the Japanese scientists reported in 1972 that TiO2 decomposes water to produce hydrogen under ultraviolet light, the photoelectrocatalytic method has attracted great attention. Photoelectrocatalytic decomposition of water hydrogen production technology, based on solar energy and water, two renewable materials, no by-products, will not pollute the environment. While photo-catalytic technology takes into account small-scale applications and large-scale development, therefore, photocatalytic decomposition of water to hydrogen production technology is the most promising research direction of solar hydrogen production.

Bismuth tungstate Bi2WO6 is an indirect band gap transition semiconductor material with a narrow band gap (2.75-2.9 eV), and the wavelength of absorbed light can be extended to the visible region (450 nm) with good chemical stability. Relative to tungsten trioxide (WO3), its valence band position is closer to the reduction potential of hydrogen, allowing the water decomposition reaction to proceed at a lower bias.

Recently, researchers have proposed a Bi2WO6 nano film with photocatalytic properties, including a Bi2WO6 nano film layer grown on a substrate composed of a Bi2WO6 nanostructure, which is a fluorine-doped tin oxide (FTO) conductive layer. The glass has a thickness of 15-60 nm, and the Bi2WO6 nano film layer has a thickness of 1500-3000 nm. The preparation process for this study is as follows:

1.Preparation Of Bismuth Iodoxyl Nanoparticle Precursor Solution

1.1 The FTO conductive glass was sequentially ultrasonicated in deionized water, acetone and ethanol solution for 10 min, washed with deionized water, and dried for use;

1.2 3.32g of potassium iodide powder and 0.9702g of cerium nitrate powder were added to 60mL of deionized water, and the pH was adjusted to 1.7 with 65-68% by volume of commercial concentrated nitric acid, and finally the iodine oxygen bismuth nanosheet precursor solution with concentration of pH=1.7 was 0.04moL/L.

2. Preparation of Iodine Oxide Bismuth Nanosheet Thin Film

The cathodic electrocomposition step was carried out by using a standard three-electrode device. The FTO conductive glass was used as the working electrode, the platinum plate electrode was used as the counter electrode, and the silver/silver chloride electrode was used as the reference electrode. The iodonium hydride nanosheet precursor solution was used as an electrodeposition solution for the cathodic electrodeposition process. Deposition was carried out for 10 min at a voltage of -0.1 V (vs. silver/silver chloride electrode). The iodonium oxide nanosheet film on the FTO was obtained.

3. Bi2WO6 Nano Thin Film Preparation

3.1 Add 1.316g sodium tungstate into 40ml deionized water to get 40ml sodium tungstate ion exchange solution with concentration 0.1mol/L. The iodonium oxide nanosheet film and the iodonium oxide film were placed face up, obliquely placed in a crystallization vessel, and an ion exchange solution was added to carry out an ion exchange process at 120 ° C for 4 hours to prepare a Bi2WO6 nano film with deionized water. Wash and dry at room temperature.

3.2 The prepared Bi2WO6 nano film was calcined, and the muffle furnace was fired at a temperature of 2°C/min, heated to 550°C for 2 h, and naturally cooled to obtain a Bi2WO6 nano film.

Nano bismuth tungstate thin film can be used as a high-efficiency photo-anode material, which can be used in photoelectrochemical cell to photo-decompose water to produce hydrogen, which can efficiently convert solar energy into clean energy, effectively alleviating the current shortage of fossil fuel and serious environmental pollution.

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