Substrate-dependent ALD of Cux on TiO2 and its performance in photocatalytic CO2 reduction

Abstract

Atomic layer deposition (ALD) technique has been proved to be an efficient method to synthesize or modify catalyst. In this study, Cu was loaded on different TiO2 substrates, pristine TiO2 and black TiO2 (denoted as H-TiO2) to achieve better CO2 photocatalytic reduction performance. Both TiO2@Cu and H-TiO2@Cu exhibited dramatic enhancement for CO and CH4 production. The peculiar phenomenon of TiO2 outperforming H-TiO2 after ALD loading was further studied by a series of characterization methods. Even though H-TiO2 showed superior performance for photocatalytic CO2 reduction than TiO2, pristine TiO2 loaded with more Cu0/+ after ALD deposition surpassed the performance of H-TiO2@Cu which possessed less amount of Cu0/+ and more Cu2+. Cu0/+ is proved to be the crucial factor for CO2 reduction and it is capable of overshadowing the influence of Ti3+ and Vo. These results indicate that not only will ALD technique significantly enhance the CO2 reduction performance after Cu deposition, but the substrate employed for loading and the chemical state of loaded material will also influence the subsequent catalytic performance. In addition, our result provides additional experiment evidence for justifying the significance of Cu0/+ in photocatalytic CO2 reduction reaction.