S-scheme heterojunction of ZnCdS nanospheres and dibenzothiophene modified graphite carbon nitride for enhanced H2 production

Abstract

g-C3N4-based photocatalysts with an intramolecular donor-acceptor structure still suffer from inadequate visible-light absorption and severe charge recombination. Constructing S-scheme heterojunction is a promising approach to address these issues. Herein, ZCS (ZnCdS nanospheres)@DBTCN (g-C3N4 modified by dibenzothiophene groups) S-scheme heterojunction photocatalyst was synthesized through a self-assembly approach. The ZCS@DBTCN material showed a superior photocatalytic H2 production activity of 8.87 mmol g–1 h–1, which is 3.46 and 2.55 times that of pure DBTCN and ZCS, respectively. This enhanced photocatalytic performance could be ascribed to the synergistic effect of intramolecular internal electric field and S-scheme heterojunction, which boosts the separation and transport of photogenerated carriers within the molecular framework and at the interface, and preserves the maximum redox capacity of the spatially separated electrons and holes. Moreover, the S-scheme charge migrate mechanism of ZCS@DBTCN was strongly evidenced by the in-situ irradiated Kelvin probe force microscopy and in-situ irradiated X-ray photoelectron spectroscopy. This study provides a protocol for designing g-C3N4-based hybrid photocatalysts with high charge separation efficiency and excellent photocatalytic activity.