Synthesis Of WO₃-TiO₂ Photoanode And Their Photoelectrochemical Properties For CO₂ Reduction

The limited supply of energy and global climate change caused by burning fossil fuels are two serious challenges faced by huamns in the future. As the burning production of fossil fuels, CO2 has caused striking environmental pollutions. Photoelectrochemical reduction of CO2 can reduce CO2 into organic substance. It can not only decrease the pressure of CO2 on the environment, but also provide a new way to alleviate the energy problem. In this paper, WO3-TiO2 composite catalysts were synthesized by coating method, and were used as photoanode for photoelectrochemical reduction of CO2, with copper foam as cathode. Compared with common CO2 reduction system, this one can reduce the hydrogen evolution reaction and the required bias, resulted in a low energy consumption and high efficiency of reduction. The main contents are as below:The WO3 powders were obtained by the calcining method, and WO3-TiO2 composite photoanode films were prepared by a coating method, and 5 wt% WO3 within WO3-TiO2 film calcinated at 450? exhibits a photocurrent density of 695 ?A/cm2 (1.19 V vs. Ag/AgCl), which is 1.5 times of pure TiO2 film. Introduction of WO3 can improve the visible light absorption ability of TiO2 photoanode and reduce the electronic transfer resistance at the interface, thus improves its photoelectrochemical properties. Then we used 5 wt% WO3-TiO2 photoanode and copper foam cathode for photoelectrochemical reduction of CO2, with an optimal generation of 929 nmol/cm2 for formic acid.A series of different oxygen vacancy WO3-x powders were obtained by hydrogen reduction process, and then WO3-x-TiO2 composite photoanodes were synthesized by coating method at room temperature. Found that the prepared WO3-x powders had uniform particle size within 50 nm. Among these, the WO2.65-TiO2 film showed a photocurrent density of 548.1 ?A/cm2 (1.19V vs. Ag/AgCl). This is due to the presence of oxygen vacancy increases the surface oxidation reaction rate of semiconductor and electron transfer rate. Moreover, oxygen vacancies can also change the forbidden band width of material so as to improve the light absorption ability of material, thus increase the photoelectric properties. For WO2.65-TiO2 photoanode combined with copper foam cathode for photoelectric catalytic reduction of CO2, when applied bias was 1.8V, and the reaction time is 3 hours, an optimal generation of 871 nmol/cm2 was obtained for formaic acid.