Unraveling the Transformation from Type-II to Z-Scheme in Perovskite-Based Heterostructures for Enhanced Photocatalytic CO<sub>2</sub> Reduction
Wentao Song, Kok Chan Chong, Guobin Qi, Yukun Xiao, Ganwen Chen, Bowen Li, Yufu Tang, Xinyue Zhang, Yingfang Yao, Zhiqun Lin, Zhigang Zou, Bin Liu
Abstract
The ability to create perovskite-based heterostructures with desirable charge transfer characteristics represents an important endeavor to render a set of perovskite materials and devices with tunable optoelectronic properties. However, due to similar material selection and band alignment in type-II and Z-scheme heterostructures, it remains challenging to obtain perovskite-based heterostructures with a favorable electron transfer pathway for photocatalysis. Herein, we report a robust tailoring of effective charge transfer pathway in perovskite-based heterostructures via a type-II to Z-scheme transformation for highly efficient and selective photocatalytic CO 2 reduction. Specifically, CsPbBr 3 /TiO 2 and CsPbBr 3 /Au/TiO 2 heterostructures are synthesized and then investigated by ultrafast spectroscopy. Moreover, taking CsPbBr 3 /TiO 2 and CsPbBr 3 /Au/TiO 2 as examples, operando experiments and theoretical calculations confirm that the type-II heterostructure could be readily transformed into a Z-scheme heterostructure through establishing a low-resistance Ohmic contact, which indicates that a fast electron transfer pathway is crucial in Z-scheme construction, as further demonstrated by CsPbBr 3 /Ag/TiO 2 and CsPbBr 3 /MoS 2 heterostructures. In contrast to pristine CsPbBr 3 and CsPbBr 3 /TiO 2, the CsPbBr 3 /Au/TiO 2 heterostructure exhibits 5.4- and 3.0-fold enhancement of electron consumption rate in photocatalytic CO 2 reduction. DFT calculations and in situ diffuse reflectance infrared Fourier transform spectroscopy unveil that the superior CO selectivity is attributed to the lower energy of *CO desorption than that of hydrogenation to *HCO. This meticulous design sheds light on the modification of perovskite-based multifunctional materials and enlightens conscious optimization of semiconductor-based heterostructures with desirable charge transfer for catalysis and optoelectronic applications.