Metal-Oxide-Mediated Subtractive Manufacturing of Two-Dimensional Carbon Nitride for High-Efficiency and High-Yield Photocatalytic H2 Evolution.

g-C3N4 is a promising visible-light-driven photocatalyst for H2 evolution reaction; however, the achievement of the high photocatalytic performance is primarily limited by the low separation efficiency of the photogenerated charge carriers and partly restricted by the slow kinetics of charge transfer. 2D g-C3N4 can significantly improve the charge generation, transfer, and separation efficiencies. The 2D g-C3N4-based Z-scheme heterostructure can further enhance the charge-carrier separation and simultaneously increase the redox ability, thereby further boosting the photocatalytic performance. Here we report a transition-metal-oxide (TMO)-mediated subtractive manufacturing process toward the large-scale synthesis of 2D g-C3N4 and the simultaneous formation of a 2D/2D TMO/g-C3N4 Z-scheme heterojunction. The TMOs serve as catalysts to facilitate the hydrolysis reaction of the bulk g-C3N4 in the presence of moist air, forming 2D g-C3N4. The resulting 2D/2D TMO/g-C3N4 catalysts, in particular, 2D/2D Co3O4/g-C3N4, exhibit high-efficiency and high-yield photocatalytic H2 evolution due to the suppression of electron-hole pair recombination and enhanced redox ability. The 2D/2D Co3O4/g-C3N4 photocatalyzes the H2 evolution with a rate of ∼370 µmol h-1 within λ > 400 nm. The external quantum efficiency of 2D/2D Co3O4/g-C3N4 at λ = 405 nm reaches 53.6%, which is among the highest values for g-C3N4-based catalysts.