Surface Modifications of Heterogeneous Photocatalysts for Photocatalytic Conversion of CO₂ by H₂O as the Electron Donor

The photocatalytic conversion of CO₂ using H₂O over heterogeneous photocatalysts has attracted worldwide attention because it enables direct solar-to-chemical energy conversion. However, further development of this technology requires solutions to overcome the low formation rates of CO₂ reduction products and their insufficient selectivity, mainly caused by the rapid charge recombination of photogenerated electron/hole pairs, competition for thermodynamically preferential H₂ evolution from H₂O, and the relatively low concentration of CO₂ on the surface of the photocatalysts. Surface modification of heterogeneous photocatalysts is crucial for improving their formation rates and selectivity. This review article introduces four strategies for designing photocatalyst surfaces for the photocatalytic conversion of CO₂ by H₂O: (I) loading of an Ag cocatalyst, (II) utilisation of cocatalysts for H₂O oxidation, (III) suppression of undesired H₂ evolution, and (IV) loading of basic materials for CO₂ adsorption. The strategies introduced in this review successfully enhanced the formation rates of the products and/or their selectivity in the heterogeneous photocatalytic conversion of CO₂ by H₂O.