Preparation Of Ga-containing Photocatalysts And Their Performance In Photoreduction Of CO₂

With a rapid development of industry and economy in the world, the consumption of carbon-rich fossil fuels such as coal, oil and natural gas is increasing. On the other hand the burning of fossil fuels resulting into the energy crisis and serious environmental issues, threatens the sustainable development for human society and attracts a high degree of attention and concern for people.CO2is one of the main products of the traditional fossil fuel combustion. High input of energy is needed for breaking the C=O due to the thermodynamic stability of CO2. The use of photocatalytic technology to reduction of CO2and water vapor into solar fuel (etc:hydrocarbon fuels) can realize energy supply by carbon cycle and is regarded as the Dream Technology in21th century with attractive prospect.Developing new photocatalysts with high photocatalytic activity to improve the CO2conversion efficiency is the key step for photoreduction CO2into practical application. For the gas phase reaction of CO2photoreduction, it contains two reaction processes:gas adsorption and catalytic conversion. It means that the gas adsorption, photo absorption and the separation and migration of charge carriers, have some effects on the rates of phtocatalytic reaction. It has been reported that elements which contain d10electronic structure (Ga and Zn etc) usually have good photocatalytic performance. In this paper, for studying the Ga-containing oxides with d10electronic structure, we prepared mesoporous Ga2O3single nanoplate with exposed (001) facet via a pseudomorphic and topotactic transformation and exploited its reaction mechanism for CO2photoreduction. To further improve the photocatalytic activity of Ga2O3nanoplate, we constructed ZnGa2O4/Ga2O3heterojunction as the built-in field can separate the photo electron and hole efficiently so as to improve the reaction rate and the selectivity of products during CO2photoreduction.We did the following works:1. Without any template or surface active agents, we successfully synthesized Ga2O3single crystal nanoplates and study the growth mechanism by controlling its morphology via variation of pH. We find that compared with commercial Ga2O3, Ga2O3nanoplates exhibited higher photocatalytic activity. We exploited and proposed reaction mechanism of CO2photoreduction over Ga2O3by FTIR and EPR.2. The efficient heterojunction of ZnGa2O4/Ga2O3was successfully synthesized by dispersing ZnGa2O4nanoparticles on the surface of single crystal Ga2O3nanoplate. The experimental results suggest that this method helps to construct a smooth interface, which favors the transport of carriers. The evaluation of CO2photoreduction shows that the heterojunction has good photocatalyic activity and selectivity. Based on the FTIR analysis, a possible reaction mechanism was proposed.