Exfoliated metal free homojunction photocatalyst prepared by a biomediated route for enhanced hydrogen evolution and Rhodamine B degradation

Abstract

g-C₃N₄ has been widely used as a smart material for photocatalytic applications. Due to insufficient solar-light absorption and fast electron–hole recombination, the photocatalytic activity of g-C₃N₄ remains a challenge for industrial applications. In this study, we prepared an exfoliated g-C₃N₄ homojunction in a single-step biomediated route, thereby addressing the major issues of g-C₃N₄. With a well exfoliated and layered sheet structure, g-C₃N₄ exhibits exceptional physical properties such as ultrahigh intrinsic carrier mobility and pronounced changes in the energy band structure due to weak van der Waals forces between C₃N₄ layers. The formation of well exfoliated sheets of g-C₃N₄ was confirmed by XRD, FESEM, TEM and AFM results. More importantly XPS confirmed the synthetic process by the biomediated route, in which some electron acceptor (–CN) groups were easily introduced at the edge of g-C₃N₄, aiding the in situ p–n homo-junction formation. The g-C₃N₄ homojunction was confirmed by Mott–Schottky analysis. This homojunction structure was proven by EIS and TRPL analysis to be highly proficient in charge transfer and separation processes. The exfoliated g-C₃N₄ homojunction showed significantly enhanced photocatalytic activity, compared to that prepared through the conventional route, due to the unique structural advantages, electron transfer, light harvesting, lower recombination rate of charge carriers and the richly available reaction sites during the photocatalytic reaction. g-C₃N₄ prepared through the one step biomediated route was able to evolve 87 μmol h⁻¹ of H₂ and degrade 90.2% of 200 ppm RhB solution, which is significantly higher than bulk g-C₃N₄ prepared through the conventional route.