Construction of Zn0.2Cd0.8S/g-C3N4 nanosheet array heterojunctions toward enhanced photocatalytic reduction of CO2 in visible light

The efficiency of photocatalytic CO2 reduction is severely limited by slow surface reaction kinetics and poor structural stability. In this study, a three-dimensional Zn0.2Cd0.8S/g-C3N4 (ZnCdS/CN) nanosheet array with type Ⅱ-scheme heterojunction structures was prepared using a mild in situ method. This heterojunction structure exhibited greatly improved carrier separation and specific surface area (45 m2 g−1), excellent stability, and broad-spectrum visible-light sensitivity. Without the use of any sacrificial agent, ZnCdS/CN20% demonstrated the highest photocatalytic efficiency of all the samples, with a CH3OH yield of 700.5 μmol·g−1·h−1. The type-Ⅱ-scheme heterojunction structure was responsible for the remarkable activity and stability because the photogenerated holes were transmitted to g-C3N4 across the heterojunction interface for the oxidation reaction, while the photogenerated electrons accumulated on Zn0.2Cd0.8S for the reduction reaction. This structure prevented oxidative corrosion on Zn0.2Cd0.8S and significantly improved the photogenerated electron–hole separation. This synthetic strategy provides new perspectives on the design and construction of efficient heterojunction photocatalysts for the solar-driven catalytic conversion of CO2.