Amorphous Co3S4 nanoparticle-modified tubular g-C3N4 forms step-scheme heterojunctions for photocatalytic hydrogen production

Abstract

An effective method to reduce the recombination rate of photogenerated electron–hole pairs was developed by the construction of heterojunctions with rationally designed photocatalysts having a matched band structure. Herein, g-C₃N₄ hexagonal tubes possessing a lower conduction band were coupled with Co₃S₄ ultra-fine nanoparticles having relatively higher positions for their conduction band. A step-scheme heterojunction was constructed between these two materials, and through this heterojunction, the spatial charge separation was boosted. The boosted spatial charge separation led to more useful electrons with a higher reduction ability that participated in a photocatalytic H₂ evolution reaction. The Co₃S₄ ultra-fine nanoparticles act as a mirror to repeatedly scatter and reflect incident light and thus enhance light utilization, and they also accelerate the spatial charge separation. The photocatalytic H₂ evolution activity of the composite catalyst reached 2120 μmol g⁻¹ h⁻¹, which was 176 times higher than that of pristine g-C₃N₄ tubes. A series of characteristics were determined to investigate the interaction that occurred between the g-C₃N₄ hexagonal tubes and the Co₃S₄ ultra-fine nanoparticles, and to study the mechanism of the formed step-scheme. This work will guide the design of step-scheme heterojunction-based photocatalysts to produce H₂ from photocatalytic water splitting.