Ultrathin and Small‐Size Graphene Oxide as an Electron Mediator for Perovskite‐Based Z‐Scheme System to Significantly Enhance Photocatalytic CO2 Reduction

The judicious design of efficient electron mediators to accelerate the interfacial charge transfer in a Z‐scheme system is one of the viable strategies to improve the performance of photocatalysts for artificial photosynthesis. Herein, ultrathin and small‐size graphene oxide (USGO) nanosheets are constructed and employed as the electron mediator to elaborately exploit an efficient CsPbBr3‐based all‐solid‐state Z‐scheme system in combination with α‐Fe2O3 for visible‐light‐driven CO2 reduction with water as the electron source. CsPbBr3 and α‐Fe2O3 can be closely anchored on USGO nanosheets, owing to the existence of interfacial strong chemical bonding behaviors, which can significantly accelerate the photogenerated carrier transfer between CsPbBr3 and α‐Fe2O3. The resultant improved charge separation efficiency endows the Z‐scheme system exhibiting a record‐high electron consumption rate of 147.6 µmol g−1 h−1 for photocatalytic CO2‐to‐CO conversion concomitant with stoichiometric O2 from water oxidation, which is over 19 and 12 times higher than that of pristine CsPbBr3 nanocrystals and the mixture of CsPbBr3 and α‐Fe2O3, respectively. This work provides a novel and effective strategy for improving the catalytic activity of halide‐perovskite‐based photocatalysts, promoting their practical applications in the field of artificial photosynthesis. An efficient halide perovskite–based all‐solid‐state Z‐scheme system is successfully fabricated by employing ultrathin and small‐size graphene oxide (USGO) as electron mediator, which achieves a record‐high electron consumption rate of 147.6 µmol g−1 h−1 for photocatalytic CO2‐to‐CO conversion, owing to the facilitation of USGO to the interfacial charge transfer between semiconductors.