Gas Bubbling Exfoliation Strategy Towards 3d G-C3n4 Hierarchical Architecture for Superior Photocatalytic H2 Evolution

Abstract

Graphitic carbon nitride (g-C3N4) shows a graphite-like layered structure, which provides a high theoretical value for solar-to-hydrogen evolution especially for a 2D nanostructure. However, conventional polycondensation induces a strong agglomeration and collapse of nanostructure, resulting in a relatively poor photocatalytic performance. To overcome this problem, we develop a gas bubbling exfoliation strategy with NH4Cl assistant to make ultrathin 2D g-C3N4 nanosheets self-assembled into a 3D macroporous network on a large scale. The hierarchical structure significantly improves the specific surface area to 176.4 m2 g-1 (11.6 times higher than the reference g-C3N4), which allows a large water/g-C3N4 interface for photocatalytic water reduction reaction. The ultrathin 2D g-C3N4 nanosheets show a thickness of about 1.4 nm, which greatly suppress photoinduced carriers recombination and enhance charge transfer at the interface. Furthermore, the doping of N and Cl is achieved during synthesis. As a result, the resulting g-C3N4 demonstrates a remarkable improvement in H2 production of 12.89 mmol g-1 h-1, which is 21 times higher than the g-C3N4 obtained from the conventional condensation method. These explorations provide a facile guidance for the quasi 3D g-C3N4 hierarchical architecture engineering even for various energy-related application.

Keywords: Photocatalyst, g-C3N4, Doping, Hierarchical structure, 3D macroporous network, Hydrogen production