Oxygenated monolayer carbon nitride for excellent photocatalytic hydrogen evolution and external quantum efficiency

Oxygen-modified monolayer g-C3N4 materials (abbreviated as O-g-C3N4) with high crystallinity in a high yield are prepared via thermal oxidation. The partial oxygenation of g-C3N4 was simultaneously achieved, providing the opportunity to collaboratively affect both structure and electron for photocatalytic hydrogen evolution. The O-g-C3N4 monolayer exhibited a production rate of ~44.37 mmol/g (~8874.7 μmol/h g) for hydrogen evolution leading to the highest external quantum efficiency (EQE) of 13.7% (at 420 nm) of the reported g-C3N4 nanosheets in a 5 h duration under visible light irradiation. More promisingly, the photocatalytic reaction proceeded for more than 25 h without performance degradation.