Photocatalytic films for efficient gas phase CO2 reduction into value-added chemicals

Abstract

A viable method to lower the atmospheric CO2 concentration is artificial photosynthesis, which converts CO2 and H2O into products with added value. Herein, the catalytic activity of thin photocatalytic films was examined in water vapor, batch, and flow reactor configurations for CO2 reduction. In addition to the experimental study, a theoretical analysis of the reaction mechanism over silica-modified amorphous TiO2 (AM-TiO2-SiO2) and indium tin oxide (ITO) photocatalysts is conducted. In the case of AM-TiO2-SiO2, the research shows that surfaces with low loading of SiO2 groups have a higher affinity for certain target molecules (T-M). This affinity accelerates adsorption and reaction but it may hinder the proceed of the reaction and lead to the deactivation of the catalyst. The oxygen vacancy (Ov) was identified as the primary reaction site for CO2 reduction to CO with a production rate of 2760±10% μmol.gcat-1.hr-1 and high selectivity in the DFT modeling of the reaction mechanism for ITO catalyst. According to the proposed reaction mechanism, the loss of Ov could be one of the causes of the ITO catalyst's deactivation. Furthermore, the effect of three different substrates with various conductivities on charge transfer and activity in the photocatalytic CO2 reduction was investigated using density functional theory (DFT) calculations, and optical and photo-electrochemical analyses. We demonstrated that a conductive substrate could enhance the photocatalytic activity of multielectron transfer reduction reactions such as CO2 reduction. Our research has implications for the design of an efficient and effective photocatalyst for gas-phase CO2 reduction.