Zinc Tungstate-Iodine Oxide Heterojunction Photocatalytic Material

As an important photocatalyst, zinc tungstate exhibits good photocatalytic activity in photolysis of water and degradation of organic pollutants. The photocatalyst exhibits strong ultraviolet photocatalytic activity in the process of degrading the rhodamine B solution. However, due to the large band gap energy of zinc tungstate, it can only be excited by ultraviolet light irradiation, and the shortcoming of photogenerated electron-hole pairs generated by photoexcitation, which limits its application in practice.

In order to make full use of sunlight, it is imperative to modify zinc tungstate. In order to overcome the shortcomings of monomer catalyst materials, some scholars have developed an efficient zinc tungstate bismuth-iodide heterojunction photocatalytic material. The material has the advantages of low cost, simple preparation process and easy mass production. It can significantly increase the separation probability of photogenerated carriers and improve the photocatalytic performance of the material.

The preparation process of zinc tungstate bismuth-iodide heterojunction photocatalytic material is as follows:

(1)Dissolve 0.219g zinc acetate and 0.330g sodium tungstate in 10 ml deionized water respectively, stir for 10 minutes, then add sodium tungstate solution to zinc acetate solution drop by drop and continue stirring, adjust the pH value of solution to 9.0 with diluted 25wt%-28wt% ammonia solution. After 20 minutes of stirring, the mixed solution was transferred to a 25 ml reactor, and then reacted at 180 ℃ for 12 hours. After natural cooling to room temperature, the products were collected, washed and dried to obtain zinc tungstate nanorods.

(2)Dissolve 0.166g potassium iodide in 20 ml deionized water, add 0.485g bismuth nitrate and continue stirring. Then 0.314g zinc tungstate nanorods were added to the above mixed solution. The molar ratio of potassium iodide to zinc tungstate was 1:1, stirred for 0.5 hours at room temperature, and heated for 2 hours in a water bath at 80 ℃. Zinc tungstate bismuth-iodide heterojunction photocatalytic material was obtained by collecting, washing and drying the products. The prepared catalyst was named ZB-1. The molar ratio of bismuth iodide to bismuth oxide is 50%.

The prepared zinc tungstate/bismuth iodide heterojunction photocatalytic material can respond well to visible light and exhibit excellent visible light photocatalytic performance. The degradation efficiency of methyl orange by zinc tungstate bismuth-iodide heterojunction photocatalytic material reaches 86% after 4 hours of visible light irradiation with wavelength greater than 420 nm. In contrast, pure zinc tungstate has almost no visible photocatalytic activity, while pure bismuth iodide has only 26% degradation efficiency.

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