Thickness‐Dependent Facet Junction Control of Layered BiOIO3 Single Crystals for Highly Efficient CO2 Photoreduction

Abstract Thin layer fabrication and crystal facet engineering favor the prompt charge transfer from bulk to the surface of a material and spatial charge separation among different facets, tremendously benefitting photocatalytic activity. However, the thickness and surface facet composition are considered as two entwined characteristics of layered materials with well‐defined and tunable shapes, which possess great promise to achieve the simultaneous manipulation of charge transfer and spatial separation. Herein, it is demonstrated that one solution for the aforementioned issue by controllably regulating the surface {010}/{100} facet junctions of a layered thickness‐tunable bismuth‐based material, BiOIO 3 . The attenuation in thickness of BiOIO 3 nanoplates shortens the diffusion pathway of charge carriers, and more importantly the tuning of nanolayer thickness renders the ratio variation of the top {010} facet to the lateral {100} facet, which dominates the spatial separation of photogenerated electrons and holes. As a result, the highest CO evolution rate from CO 2 reduction over BiOIO 3 nanoplates with the optimal thickness and ratio of exposed facets reaches 5.42 µmol g −1 h −1 , over 300% that of the bulk counterpart (1.77 µmol g −1 h −1 ). This work paves a new way for governing charge movement behaviors on the basis of the synergistic engineering of layer structure and exposing facets.