In situ fabrication of reduced graphene oxide/mesoporous g-C3N4 nanosheets with excellent visible light activity

Abstract

Severe energy shortage and environmental pollution prompt researchers to develop metal-free semiconductors as high-performance photocatalysts for wastewater treatment. Herein, highly efficient visible light-driven photocatalysts, reduced graphene oxide/mesoporous g-C3N4 (rGO/mpg-C3N4) nanosheets are in situ fabricated by surfactant-directed assembly of graphene oxide and melamine via an evaporation-induced self-assembly approach before a solid-state transformation. The mass ratio of rGO to mpg-C3N4 in final nanosheets is tailored in a wide range of 1–76%. All rGO/mpg-C3N4 nanosheets are covalently linked, highly porous, display improved separation of electron-hole pairs, narrowed bandgap and modulated band structure. And they are superior to Degussa’s P25 and g-C3N4 in the degradation of methylene blue under visible light irradiation. The elaborately fabricated rGO/mpg-C3N4-15% gives the highest specific rate constant (1.005 min−1 g−1) of any g-C3N4 composite catalyst. Mechanism study reveals that the best performance is originated from the increased h+ and −O2 species, linking to the strong interaction between rGO and mpg-C3N4. Mesostructure and proper rGO ratio, and their ensemble effect, are also responsible for the best activity, since merits including superior mass transfer, improved charge carrier separation and excellent visible light utilization are integrated.