Wavelength-sensitive photocatalytic H2 evolution from H2S splitting over g-C3N4 with S,N-codoped carbon dots as the photosensitizer

Activity enhancement of S,N codoped carbon dots (S,N-CDs) on g-C 3 N 4 for photocatalytic H 2 evolution from H 2 S splitting is heavily dependent on the wavelength of the incident light due to their dominant photosensitization effect. • S,N-CDs improve the photocatalytic activity of g-C 3 N 4 for H 2 S splitting by 38 times. • S,N-CDs selectively improve the activity of g-C 3 N 4 and do best at 460 nm. • Photosensitization plays the dominant role for activity enhancement. • Energy level match of S,N-CDs and g-C 3 N 4 is vital for effective H 2 evolution. Photocatalytic splitting of hydrogen sulfide (H 2 S) for hydrogen evolution is a promising method to solve the energy and environmental issues. In this work, S,N-codoped carbon dots (S,N-CDs)/graphitic carbon nitride (g-C 3 N 4 ) nanosheet is synthesized by hydrothermal method as an efficient photocatalyst for the decomposition of H 2 S. In addition to the characterization of the morphology and structure, chemical state, optical and electrochemical performances of S,N-CDs/g-C 3 N 4 , hydrogen evolution tests show that the activity of g-C 3 N 4 is improved by introducing S,N-CDs, and the enhancement depends strongly on the wavelength of incident light. The photocatalytic hydrogen production rate of S,N-CDs/g-C 3 N 4 composite reaches 832 μmol g −1 h −1 , which is 38 times to that of g-C 3 N 4 under irradiation at 460 nm. Density functional theory calculations and electron paramagnetic resonance as well as photoluminescence technologies have altogether authenticated that the unique wavelength-dependent photosensitization of S,N-CDs on g-C 3 N 4 ; meanwhile, a good match between the energy level of S,N-CDs and g-C 3 N 4 is pivotal for the effective photocatalytic activity. Our work has unveiled the detailed mechanism of the photocatalytic activity enhancement in S,N-CDs/g-C 3 N 4 composite and showed its potential in photocatalytic splitting of H 2 S for hydrogen evolution.