Dual role of a g-C3N4/carbon intra-Schottky junction in charge carrier generation and separation for efficient solar H2 production

Abstract

Graphitic carbon nitride (g-C₃N₄) has been considered as a prominent metal-free visible light-driven photocatalyst for solar water splitting. However, the rapid recombination of photogenerated charge carriers massively limits its photocatalytic performance. Herein, we have constructed an intra-Schottky junction in g-C₃N₄ by enriching it with carbon via a solid-state calcination method to improve the charge carrier separation efficiency for solar photocatalytic H₂ production. Enriching of carbon in g-C₃N₄ led to the effective overlapping between 2p orbitals of both nitrogen and carbon, thereby inducing an intra-Schottky junction by increasing the C/N ratio as confirmed by XPS analysis. Importantly, compared to bare g-C₃N₄, ∼6-fold enhancement on the photocatalytic H₂ production rate was achieved with 5 wt% carbon enriched g-C₃N₄ photocatalyst. The enhanced photocatalytic activity was mainly attributed to efficient charge carrier generation and separation through an intra-Schottky junction as revealed by photoluminescence, photocurrent and impedance studies. Moreover, the C-enriched g-C₃N₄ photocatalyst has shown higher photostability and photocatalytic H₂ production activity compared to that in previous reports. Thus, we trust that the present study may provide an insight into the fabrication of an intra-heterojunction for enhanced photocatalysis.