Revealing the Spatial Shielding Effect of Interfacial Water Molecules in Photocatalytic CO₂ Reduction from Overall Water Splitting

In this context, a Al₂O₃ doped SrTiO₃ (Al:SrTiO₃) was synthesized via the molten salt method. The spatial separation active sites of the hydrogen evolution and the CO₂ reduction in photocatalysis were revealed by using absorbed H₂ as a probe, which indicated that CoOOH could be the photocatalytic CO₂ reduction active site while RhCrO_<i>x</i> could serve as the main site for hydrogen species activation and generation. The photocatalytic CO₂ reduction could be determined by the spatial-temporal transfer of active hydrogen species coupled with carriers, from the interface of RhCrO_<i>x</i>-Al:SrTiO₃ to CoOOH-Al:SrTiO₃ probably. More importantly, the competitive relationship between liquid water molecules, active hydrogen species, and CO₂ was proved, indicating that the water film may hinder the spatial-scale migration of active hydrogen species and CO₂ absorption. This work explored photocatalytic CO₂ reduction from overall water splitting systems and emphasized the importance of the spatial shielding effect of interfacial water molecules.