Co3O4 Nanosheet/g-C3N4 Hybrid Photocatalysts for Promoted H2 Evolution

Abstract

Co3O4 is an attractive semiconductor in the photocatalytic field due to its proper band gap; however, its energy level structure is mismatched for H2 evolution. Herein, the Co3O4-based photocatalysts, Co3O4 nanosheet/g-C3N4 hybrids, were successfully prepared by an ultrasonic self-assembly method for enhanced photocatalytic H2 evolution. The optimized hybrid with 20 wt % g-C3N4, 20-CNCo, displayed the best photocatalytic performances, and the average H2 evolution rate was 134.6 μmol·g–1·h–1. The enhanced photocatalytic H2 evolution activities of 20-CNCo were due to the formation of heterojunctions between Co3O4 nanosheets and g-C3N4, which can increase the optical absorption ability, promote the separation of photogenerated charges, accelerate the electron transfer, and prolong the lifetime of the excited electrons. Moreover, following the unique step-scheme (S-scheme) charge transfer mechanism, the strong redox ability of the Co3O4 nanosheet/ g-C3N4 hybrid was retained, which was beneficial to the H2 evolution. This work provides strategies for designing active catalysts for photocatalytic reactions.