Stacking Engineering of Heterojunctions in Half-Metallic Carbon Nitride for Efficient CO₂ Photoreduction

Enhancing charge separation in semiconductor photocatalysts is a major challenge for efficient artificial photosynthesis. Herein, a compact heterojunction is designed by embedding half-metallic C(CN)₃ (hm-CN) hydrothermally in BiOBr (BOB) as the backbone. The interface between hm-CN and BOB is seamless and formed by covalent bonding to facilitate the transmission of photoinduced electrons from BOB to hm-CN. The transient photocurrents and electrochemical impedance spectra reveal that the modified composite catalyst exhibits a larger electron transfer rate. The photocatalytic activity of hm-CN/BOB increases significantly as indicated by a CO yield that is about four times higher than that of individual components. Density-functional theory calculations verify that the heterojunction improves electron transport and decreases the reaction energy barrier, thus promoting the overall photocatalytic CO₂ conversion efficiency. The half-metal nitride coupled semiconductor heterojunctions might have large potential in artificial photosynthesis and related applications.