Ultra-thin graphene/g-C3N4 nanosheets with in-plane heterojunction for enhanced visible-light photocatalytic hydrogen evolution performance

Abstract

ABSTRACT Ultra-thin graphene/g-C3N4 nanosheets (CN/G) with in-plane heterojunction were prepared by facial two-step thermal condensation of urea and glucose under mild conditions to improve photocatalytic hydrogen evolution under visible-light irradiation. The characterisation indicated that graphene was connected to the end of g-C3N4. The thermal exfoliation process can transform the bulk structure of g-C3N4 into ultra-thin nanosheets. Consequently, photocatalytic activity for hydrogen evolution rate of CN/G-0.1 was 704 µmol g–1 h–1, about 14 times higher than that of pure g-C3N4 under visible light irradiation (λ > 420 nm). CN/G-0.1 also exhibited high stability from the cycling tests for 18 h and superior photocatalytic properties at 500 nm. In-plane graphene modification can significantly enhance visible-light absorption and promote photogenerated electron-hole pair separation. On the other hand, ultra-thin nanosheets can increase specific surface area (153.8 m2 g–1) and provide abundant active sites. This study provides a suitable method to prepare g-C3N4 based on highly efficient photocatalysts for metal-free photocatalytic hydrogen evolution.