Nanoarchitecture engineering of crumpled polymeric carbon nitride nanosheets for efficient visible-light photocatalytic CO2 reduction

Polymeric carbon nitride nanosheets with few layers have emerged as a new category of semiconductor materials which are promising for photocatalytic applications because of their unique optical and electronic characteristics. The texture and optical–electronic properties of the nanosheets significantly influence the photocatalytic activities. In this study, a series of crumpled polymeric carbon nitride nanosheets was prepared via a facile stepwise pyrolytic strategy and a time-dependent pyrolysis process. The as-obtained nanosheets exhibit a sequential change in morphology from a continuous-aggregation architecture to discrete nanosheets with prolonged thermal-treatment time. The nanosheets with the continuous-aggregation architecture, consisting of small curved nanosheet subunits are laterally large; thus, they can provide numerous reactive sites for surface reactions and awaken intrinsic n → π* electron transitions to promote photocatalytic activity. The optimum crumpled polymeric carbon nitride nanosheet is formed after 2 h of thermal condensation, and it demonstrates efficient CO2-conversion performance with the highest CO-evolution rate of 1287 µmol g−1h−1, which is 7 times more than that of pristine polymeric carbon-nitride nanosheets. This work provides an opportunity to significantly understand the roles of texture and optical–electronic properties in improving the photocatalytic activities of polymeric carbon-nitride nanosheets.