DFT Modeling of CO2 Adsorption and HCOO• Group Conversion in Anatase Au-TiO2-Based Photocatalysis.

Abstract

Due to the merits of carbon circulation and hydrocarbon production, solar-assisted photocatalysis has been regarded as an ideal option for securing a sustainable future of energy and environment. In the photocatalytic carbon cycle process, surface reactions including the adsorption of CO2 and the conversion of CO2 into CH4, CH3OH, etc. are crucial to be examined ascribed to their significant influence on the performance of the photocatalysis. Because the conversion reaction starts from the formation of HCOO•, the density functional theory (DFT) model was established in this study to investigate the micromechanism of CO2 adsorption and the conversion of CO2 to HCOO• group in the anatase Au-TiO2 photocatalytic system. The CO2 adsorption bonding in six configurations was simulated, on which basis the effects of the proportion of water molecules and the lattice temperature increase due to the local surface plasmon resonance (LSPR) on the photocatalytic CO2 adsorption and conversion were specifically analyzed. The results show that the experimental conditions that water molecules are released before CO2 are favorable for the formation of the adsorption configuration in which HCOO• tends to be produced without the need of reaction activation energy. This is reasonable since the intermediate C atoms do not participate in bonding under these conditions. Moreover, Au clusters have an insignificant influence on the adsorption behaviors of CO2 including the adsorption sites and configurations on TiO2 surfaces. As a result, the reaction rate is reduced due to the temperature increase caused by the LSPR effect. Nevertheless, the reaction maintains a very high rate. Interestingly, configurations that require activation energy are also possible to be resulted, which exerts a positive influence of temperature on the conversion rate of CO2. It is found that the rate of the reaction can be improved by approximately 1–10 times with a temperature rise of 50 K above the ambient.