Au depositing and Mg doping synergistically regulates an In2O3 photocatalyst for promoting CO2 reduction and CH4 exclusive generation

The photocatalytic reduction of carbon dioxide (CO2) into methane (CH4) is of great significance in the field of energy conversion. In this study, magnesium–gold (Mg–Au) bimetallic-modified indium oxide (In2O3) microspheres were synthesized using a hydrothermal method combined with self-reduction. The introduction of Mg doping resulted in a transformation of CO2 reduction products from a mixture (CO and CH4) to a single CH4 product. Furthermore, the subsequent modification with Au nanoparticles (4Au/2Mg–In2O3, 24.5 μmol g−1 h−1) led to a remarkable 12-fold increase in CH4 production compared with pure In2O3 (2.1 μmol g−1 h−1). This enhancement can be attributed to the lowered conduction band position of In2O3 caused by Mg doping, which directs the photogenerated electrons towards the reduction of CO2 to CH4. The presence of Au nanoparticles further facilitates the effective activation of CO2. Moreover, the specific adsorption of CO2 by Mg also contributes to the CO2 reduction reaction. The bimetallic functional site modification strategy employed in this study provides a meaningful approach to enhance the performance of photocatalysts for CO2 reduction.