Boosted CO2 Photoreduction Performance by CdSe Nanoplatelets via Se Vacancy Engineering

Abstract 2D metal‐chalcogenide nanoplatelets (NPLs) exhibit promising photocatalysis properties due to their ultrathin morphology, high surface‐to‐volume ratio, and enhanced in‐plane electron transport mobility. However, NPLs, especially cadmium chalcogenides, encounter challenges in CO 2 photoreduction due to insufficient solar energy utilization and fast recombination of photogenerated charge carriers. Defect engineering offers a potential solution but often encounters difficulties maintaining structural integrity, mechanical stability, and electrical conductivity. Herein, by taking two monolayers (2ML) CdSe NPLs as a model system, selenium (Se) vacancies confined in atomic layers can enhance charge separation and conductivity. A straightforward approach to create Se vacancies in various monolayers CdSe NPLs (2, 4, and 5ML) has been developed, enabling efficient CO 2 photoreduction with a 4‐fold increase in CO generation compared to their defect‐free counterparts. Significantly, accounting for higher charge density and efficient carrier transport due to Se vacancies, defective 2ML CdSe NPLs (V Se ‐2ML CdSe) exhibit CO evolution performance up to 2557.5 µmol g − ¹ h − ¹ with no significant decay over 5 h, which is an order of magnitude higher than that of common semiconductor catalysts. This study establishes a practical way to design advanced 2D semiconductor photocatalysts to achieve efficient CO 2 photoreduction via defect engineering.