Thin In-Plane In 2 O 3 /ZnIn 2 S 4 Heterostructure Formed by Topological-Atom-Extraction: Optimal Distance and Charge Transfer for Effective CO 2 Photoreduction.

Exploitation of atomic-level principles to optimize the charge transfer on ultrathin 2D heterostructures is an emerging frontier in relieving the energy and environmental crisis. Herein, a facile "topological-atom-extraction" protocol is disclosed, i.e., selective extraction of Zn from ultrathin half-unit-cell ZnIn 2 S 4 (HZIS) can embed thin In 2 O 3 domain into 1.60 nm thick HZIS layer to create an atomically thin in-plane In 2 O 3 /HZIS heterostructure. Thanks to the optimal distance and capability of charge separation, the in-plane In 2 O 3 /HZIS heterostructure is among the best ZnIn 2 S 4 -based CO 2 reduction reaction (CRR) photocatalysts, and indeed demonstrates a significant increase (from 6.8- to 128-fold) in CO production rate compared with those of out-plane ZIS@In 2 O 3 and out-plane In 2 O 3 -HZIS calcined heterostructures. Density Functional Theory simulation reveals that whereas the out-plane heterostructure has a much smaller ∆q of 0.2-0.25 e, the in-plane heterostructure with "zero distance contact" has an optimal ∆q of 1.05 e between In 2 O 3 and HZIS that induces remarkable charge redistribution on the in-plane heterojunction interface and creates local electric field confined within the ultrathin layer. The charge redistribution efficiently directs the charge-carrier separation in S-scheme photocatalytic system and endows long-lifetime carrier to CRR active HZIS. The findings demonstrate the strong versatility of engineering atomic-level heterojunctions for efficient catalysts design.