Gas-Phase Photocatalytic Coprocessing of CO2 – H2O(v) to Energy Products Promoted by the n,n-Junction In2O3@g-C3N4 under VIS-Light

Carbon dioxide capture and utilization is a strategic technology for moving away from fossil-C. The conversion of CO2 into fuels demands energy and hydrogen that cannot be sourced from fossil-C. Co-processing of CO2 and water under solar irradiation will have a key role in the long-term for carbon-recycling and energy products production. This article discusses the synthesis, characterization and application of the two-phase composite photocatalyst, In2O3@g-C3N4, formed by thermal condensation of melamine in the presence of indium(III)nitrate. The composite exhibits a n,n-heterojunction between two n-type semiconductors, g-C3N4 and In2O3, leading to a more efficient charge separation. The composite has a flat band potential enabling it to effectively catalyze the reduction of CO2 in the gas phase to produce CO, CH4 and CH3OH. While the composite‘s overall photocatalytic efficiency is comparable to that of neat g-C3N4, its ability to promote multielectron-transfer and Proton Coupled to Electron Transfer (PCET) suggests that there is a potential for further optimization of its properties. The use of labelled 13CO2 has allowed us to clearly exclude that the reduced species are derived from the photocatalyst decomposition or the degradation of contaminants.