Recent advances in and comprehensive consideration of the oxidation half reaction in photocatalytic CO 2 conversion

Photocatalytic conversion of CO 2 into value-added chemicals is a promising method to tackle the global warming issue and ease the need for sustainable energy. To date, much effort has been devoted to improving the electron behavior of the reduction process for effective CO 2 reduction. However, it is often overlooked that the simultaneous control of electrons and holes is more meaningful and beneficial for an overall photocatalytic reaction, since the two half reactions driven respectively by electrons and holes are equally important. Considering that much less attention has been paid to the oxidation half reaction, this review specifically highlights the approaches and strategies for promoting the oxidation half reaction that accompanies CO 2 conversion, which can in turn improve the CO 2 photoreduction performance. In detail, a comprehensive discussion on regulating the hole behavior ( e.g. lifetime and driving force) is presented in three parts, viz . materials design (element modification, oxidation co-catalysts, and Z-scheme structures), electron donors (H 2 O and sacrificial electron donors), and reaction system management (high value-added oxidation reaction). We anticipate that this review will offer a systematic summary of the past achievements and general considerations for the oxidation half reaction occurring during CO 2 reduction, which will provide possible routes and/or implications for scientists to further improve the CO 2 conversion efficiency.