Constructing Built-in Electric Field in Ultrathin Graphitic Carbon Nitride Nanosheets by N and O Codoping for Enhanced Photocatalytic Hydrogen Evolution Activity.

Abstract

Codoping of N and O in ultrathin graphitic carbon nitride (g-C3 N4 ) nanosheets leads to an inner electric field. This field restrains the recombination of photogenerated carriers and, thus, enhances hydrogen evolution. The layered structure of codoped g-C3 N4 nanosheets (N-O-CNNS) not only provides abundant sites of contact with the reaction medium, but also decreases the distance over which the photogenerated electron-hole pairs are transported to the reaction interface. Quantum confinement in the ultrathin structure results in an increased bandgap and makes the photocatalytic reaction more favorable than bulk g-C3 N4 . Under visible light irradiation, N-O-CNNS with 3 wt% Pt achieves a hydrogen evolution rate of 9.2 mmol g-1 h-1 and a value of 46.9 mmol g-1 h-1 under AM1.5 with 5 wt% Pt. Thus, this work paves the way for designing efficient nanostructures with increased separation/transfer efficiency of photogenerated carriers and, hence, increased photocatalytic activities.