A review: Effect of nanostructures on photocatalytic CO₂ conversion over metal oxides and compound semiconductors

Photo-conversion of CO₂ into valuable solar fuels under the light irradiation is one of the most environmentally-friendly and economical technologies for reducing the CO₂ emissions. Nanostructured metal oxides and compound semiconductors have been applied as photocatalysts for CO₂ conversion. Especially, nanoparticulate and nanoporous materials have been studied extensively as photocatalysts owing to their reduced dimensions for electron transport, high surface areas, catalytic activity, and shorter diffusion pathway for the reactants. Transition metal oxides have long been studied as photocatalysts, however, these materials show low CO₂ conversion efficiencies because of their wide band gap, which results in poor light absorption characteristics in the visible range. To improve the photocatalytic activity of CO₂ conversion, alternative compound semiconductors with high visible absorption light absorption properties have been considered as photocatalysts for CO₂ conversion. In this study, the effect of nanostructures on the photocatalytic conversion of CO₂ to other chemicals on transition metal oxides and compound semiconductors are compared and the promising research directions to design photocatalysts for CO₂ conversion performance enhancement are proposed.