Photocatalytic hydrogen generation from a methanol–water mixture in the presence of g-C3N4 and graphene/g-C3N4.

Graphitic carbon nitride (g-C₃N₄), possessing high thermal and chemical stability, non-toxicity, facile synthesis, and low band gap energy is a promising candidate for photocatalytic applications. In this study, bulk and exfoliated g-C₃N₄ were synthesised from different precursors (melamine and urea). Moreover, the surface of bulk g-C₃N₄ and exfoliated g-C₃N₄ was modified with graphene (0.5 wt% and 1 wt%) aiming to obtain a prolonged carrier lifetime. The effect of g-C₃N₄ synthesis from various precursors and the influence of graphene content on the photocatalytic activity during the degradation of a water–methanol mixture under UVC irradiation were examined, in comparison to commercial P25. Hydrogen, methane and carbon monoxide were the decomposition products; hydrogen was the main product of decomposition, whereas CH₄ and CO resulting from the reduction of CO₂ were generated in a significantly smaller amount. All the produced photocatalysts, whether pure or modified with graphene, exhibited higher activity than the commercial photocatalyst P25. [ABSTRACT FROM AUTHOR]