Biomass Carbon Quantum Dots Cooperating Graphitic Carbon Nitride for Efficient Photocatalytic Hydrogen Evolution

In this work, a new kind of biomass carbon quantum dots (CQDs) from Ulva prolifera was synthesized by the hydrothermal method. A series of CQDs modified graphitic carbon nitride (CQDs/g‐C 3 N 4 ) photocatalysts were prepared by thermal polymerization. The hydrogen evolution rate increases from 310.2 to 1173.2 µmol g −1 h −1 by CQDs loading. Through dosage optimization, the highest rate of 4‐CQDs/g‐C 3 N 4 reaches 2302.1 µmol g −1 h −1 under visible light. CQDs loading increases the specific surface area of g‐C 3 N 4 , which provides more active sites for photocatalysis. Furthermore, electrochemical and photophysical studies substantiate that introducing CQDs to g‐C 3 N 4 can accelerate charge transfer process and inhibit the recombination of free charges. Notably, 4‐CQDs/g‐C 3 N 4 photocatalyst shows good operation stability in cycle tests.