Construction of a heterojunction with fast charge transport channels for photocatalytic hydrogen evolution via a synergistic strategy of Co-doping and crystal plane modulation.

Carrier spatial separation efficiency and active electron density are the key factors affecting photocatalytic hydrogen evolution activity. Heterojunction catalysts with fast charge separation and directed electron transport systems were successfully prepared by a synergistic modification strategy of transition metal (Co) doping and crystal plane modulation. The optimized electronic structure and enhanced reaction kinetics enabled unidirectional electron transfer. Photocatalytic results show that CdS(002)/Co-C ₃ N ₄ exhibits remarkable hydrogen evolution activity (991.2 μmol h ^-1 g ^-1 ) in the absence of a co-catalyst, which is 37.0 and 3.4 times higher than that of C ₃ N ₄ (26.8 μmol h ^-1 g ^-1 ) and Co-C ₃ N ₄ (294.6 μmol h ^-1 g ^-1 ), respectively. Density functional theory (DFT) calculations indicate that the enhanced catalytic activity of CdS(002)/Co-C ₃ N ₄ is attributed to the reduced electron-hole recombination rate and the increased electron density at the active site. This work provides a new idea for the design of photocatalysts with directed charge transport channels from the perspective of re-optimizing heterojunctions.