ZnO-Au-SnO ₂ Z-scheme photoanodes for remarkable photoelectrochemical water splitting

For the first time a ZnO nanorod-based Z-scheme heterostructure system was proposed and realized for efficient photoelectrochemical water splitting. The samples were prepared by depositing a thin layer of SnO ₂ on the Au surface of Au particle-decorated ZnO nanorods. For ZnO-Au-SnO ₂ nanorods, the embedded Au can mediate interfacial charge transfer by promoting electron transfer from the conduction band of SnO ₂ to the valence band of ZnO. This vectorial charge transfer resulted in the situation that the photoexcited electrons accumulated at ZnO while the photogenerated holes concentrated at SnO ₂ , giving ZnO-Au-SnO ₂ substantially high redox powers. Time-resolved photoluminescence spectra suggested that the interfacial charge transfer across the ZnO/Au/SnO ₂ interface was significantly improved as a result of the Z-scheme charge transfer mechanism. With the substantially high redox powers and significantly improved interfacial charge transfer, ZnO-Au-SnO ₂ nanorods performed much better as a photoanode in photoelectrochemical water splitting than pristine ZnO, plasmonic Au-decorated ZnO and type-II SnO ₂ -coated ZnO nanorods did. The present study has provided a viable approach to exploit Z-scheme photoanodes in the design of efficient artificial photosynthesis systems for solar energy conversion.