Gas bubbling exfoliation strategy towards 3D g-C₃N₄ hierarchical architecture for superior photocatalytic H₂ evolution

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 applications.