Effect of carbon and nitrogen double vacancies on the improved photocatalytic hydrogen evolution over porous carbon nitride nanosheets

Porous carbon nitride nanosheets with carbon and nitrogen double vacancies have been synthesized by a soft template-supported one-pot method. Besides their highly defined and unambiguous structure, they also show minimal thickness and high crystallinity. This porous carbon nitride exhibits great enhancement in photocatalytic hydrogen evolution activity (297.6 μmol h−1), which is 9.6 times higher than 31.2 μmol h−1 of the pristine one. An apparent quantum yield of 12.7% at 420 nm for hydrogen production can be achieved over these porous nanosheets. The detailed investigation suggests that there are carbon vacancies along with nitrogen vacancies. Besides nitrogen vacancies, carbon vacancies also play a positive role in the improvement of hydrogen evolution. In addition, the photocatalytic performance especially hydrogen evolution increases with the increase of the C/N ratio.