Highly selective photocatalytic CO2 reduction into CO and methane (CH4) by water vapor is achieved on elaborately designed hollow sphere-based TiO2/SrTiO3 heterostructures. The synthesized three-dimensional hierarchical hollow multi-shelled TiO2/SrTiO3 spheres (HoMSs-TS) are an assembly of well-organized shells composed of interconnected anatase TiO2 and perovskite SrTiO3 nanoparticles (NPs) with an average size of ∼22 nm for each NP. The heterojunctions between TiO2 and SrTiO3 provide synergistic enhancement of the charge transfer and separation process, which is critically important in the selective photocatalytic CO2 reduction reaction (CO2RR). Moreover, this hierarchical structure features multiple porous subunits, which not only serve to maximize light utilization, but also facilitate mass transport during the photocatalytic process. These advantages empower the HoMSs-TS to effectively suppress hydrogen evolution and ease the selective production of 465 and 4.6 μmol g−1 of CO and CH4, respectively, over the course of a 24 h reaction.
