Three-Dimensional Hierarchical g‑C₃N₄ Architectures Assembled by Ultrathin Self-Doped Nanosheets: Extremely Facile Hexamethylenetetramine Activation and Superior Photocatalytic Hydrogen Evolution

Photocatalytic hydrogen evolution has broad prospects as a clean solution for the energy crisis. However, the rational design of catalyst complex, the H₂ evolution efficiency, and the yield are great challenge. Herein, three-dimensional hierarchical g-C₃N₄ architectures assembled by ultrathin carbon-rich nanosheets (3D CCNS) were prepared via an extremely facile hexamethylenetetramine activation approach at the bulk scale, indicating the validation of scale-up production process. The two-dimensional ultrathin carbon-rich nanosheets were several hundred nanometers in width but only 5–6 nm in thickness and gave rise to a unique 3D interconnected network. The unique composition and structure of the nanosheets endow them with a remarkable light absorption spectrum with the tunable band gap, high electrical conductivity, fast charge separation, and large surface areas with abundant reaction active sites, and thus significantly improved H₂ production performance. As high as ∼7.8%, quantum efficiency can be achieved by irradiating 3D CCNS at 420 nm with a H₂ evolution rate >2.7 × 10⁴ μmol/g/h, which is ∼31.3 times higher than that of the pristine g-C₃N₄. Our work introduces an extremely facile route for mass production of doping modified 3D g-C₃N₄-based photocatalyst with excellent H₂ evolution performances.