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

Abstract

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.