Co-Atomic Interface Minimizing Charge Transfer Barrier in Polytypic Perovskites for CO₂ Photoreduction

Heterojunctions, known for their decent separation of photo-generated electrons and holes, are promising for photocatalytic CO₂ reduction. However, a significant obstacle in traditional post-assembled heterojunctions is the high interfacial barrier for charge transfer caused by atomic lattice mismatch at multiphase interfaces. Here, as research prototypes, the study creates a lattice-matched co-atomic interface within CsPbBr₃-CsPb₂Br₅ polytypic nanocrystals (113-125 PNs) through the proposed in situ hybrid strategy to elucidate the underlying charge transfer mechanism within this unique interface. Compared to CsPbBr₃ nanocrystals, the 113-125 PNs exhibit a remarkable 3.6-fold increase in photocatalytic CO₂ reduction activity (173.3 µmol^-1 g^-1 within 5 h). Furthermore, Kelvin probe force microscopy results reveal an increase in the built-in electric field within this lattice-matched co-atomic interface from 43.5 to 68.7 mV, providing a stronger driving force for charge separation and directional migration. Additionally, ultrafast transient absorption spectroscopy uncovers the additional charge carrier transfer pathways across this lattice-matched co-atomic interface. Thus, this unique co-atomic interface significantly promotes the interfacial electronic coupling and mitigates the charge transfer barrier, thus facilitating efficient charge separation and transfer. These insights underscore the importance of interfacial structure in heterojunction design and comprehending the intricate interplay between interface and carrier dynamics.