Nitrogen doping of indium oxide for enhanced photocatalytic reduction of CO2 to methanol

Herein, the nitrogen-doped indium oxide (N-In2O3) photocatalyst was confirmed to be highly active and stable for photocatalytic reduction of CO2 to methanol in an aqueous solution at ambient conditions. The efficiency of N-In2O3 in producing methanol can be flexibly improved by tuning the nitrogen doping content. The highest formation rate of methanol reaches to 394 μmol gcat-1 h-1, with a methanol selectivity of 63%, at a nitrogen doping content of 3.74%. Nitrogen doping generates mid-gap energy states and reduces the bandgap of In2O3, thus boosting photon absorption and electron-hole separation. Nitrogen doping creates more oxygen vacancies on In2O3, thus forming more active sites for CO2 adsorption and conversion. Nitrogen doping also enhances the activity of the surface frustrated Lewis pairs (SFLPs), which further promotes CO2 adsorption and activation. The multiple-role of nitrogen doping results in the highly active and stable photocatalytic reduction of CO2 to methanol.