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.
We would like to express our gratitude to the Algerian Ministry of Higher Education and Scientific Research for funding Wassila TOUATI's visit to the University of Aveiro, through the National Exceptional Scholarship Program (PNE). David Maria Tobaldi acknowledges the project EleGaNTe−PON ARS01_01007. R. A. gratefully acknowledges the support from the Spanish MICINN (PID2019-104739GB-100/AEI/10.13039/501100011033), the Government of Aragon (project DGA E13-20R) and European Union H2020 program “ESTEEM3” (823717). The TEM studies were conducted at the Laboratorio de Microscopias Avanzadas, Universidad de Zaragoza, Spain. Kamila Kočí thanks the EU structural funding in the Operational Programme Research, Development and Education, project No. CZ.02.1.0./0.0/0.0/17_049/0008419 “COOPERATION”, Large Research Infrastructure ENREGAT (project No. LM2018098).