Counteracting Blueshift Optical Absorption and Maximizing Photon Harvest in Carbon Nitride Nanosheet Photocatalyst

Blueshift of optical absorption and corresponding widening of the bandgap is a fundamental problem with 2D carbon nitride nanosheets (CNNS). An additional problem is low quantum yields (<9%) due to higher loss of absorbed photons. These problems impose a significant restriction to photocatalytic performance of CNNS. Therefore, the synthesis of narrow bandgap CNNS with high quantum efficiency is of pressing research importance. This contribution reports melem-derived narrow bandgap CNNS with a record-low bandgap of 2.45 eV. The narrowing in bandgap comes with improved optical absorption and use of visible-light photons together with excellent charge transport dynamics. This is demonstrated by a record high hydrogen evolution rate of 863 µmol h^-1 with apparent quantum efficiency of 16% at 420 nm.