Photocarrier Dynamics Regulation by Constructing a 2D ZnIn2S4 Nanosheet Array with Highly Exposed Zn Vacancies for Efficient Solar-Driven CO2 Conversion

The solar-driven CO2 conversion efficiency based on semiconductor photocatalysts is severely limited by the fast recombination of photocarriers outcompeting the sluggish surface redox reaction. Herein, we demonstrate a cooperative strategy to optimize the photocarrier dynamics in a CO2 conversion photocatalyst by combining micromorphology design with defect engineering. We constructed a two-dimensional (2D) hexagonal ZnIn2S4 nanosheet array with highly exposed basal planes and Zn vacancies (denoted 2D VZn-ZIS). We show that Zn vacancies on the Zn–S terminal of basal planes introduce a defect level near the valence band, making Zn vacancies simultaneously act as photohole capture sites and surface active sites, while photoelectrons in the conduction band preferentially accumulate on the highly exposed In–S terminal of 2D VZn-ZIS to drive the CO2 reduction reaction. As a result, highly efficient spatial separation of photogenerated electrons and holes with prolonged lifetimes as well as the accelerated surface reaction dynamics can be achieved in 2D VZn-ZIS, which gives rise to high solar-driven CO2 conversion efficiency with the CO production rate reaching 441 μmol g–1 h–1. This work sheds light on combining the microstructure design and defect engineering to optimize photocarrier dynamics for next-generation semiconductor photocatalysts for solar fuel conversion.