Oxygen doping induced intramolecular electron acceptor system in red g-C3N4 nanosheets with remarkably enhanced photocatalytic performance

Abstract

The enhancement of the photocatalytic activity of graphitic carbon nitride (g-C3N4) depends on the rational design of its visible-light harvesting and charge separation/migration properties. Herein, an oxygen doping-induced intramolecular electron acceptor system enabling n→π* electronic transitions in red g-C3N4 nanosheets (Eg ∼ 1.89 eV) was prepared via copolymerization with nitrilotriacetic acid (NTA) and urea. The n→π* electronic transition can be controllably tuned, thus broadening the absorption spectrum of the system to ∼750 nm. Simultaneously, doping with oxygen which acts as an electron acceptor, accelerates in-plane charge separation and migration. Moreover, this strategy was confirmed experimentally to be scalable for industrial mass production. Experiments and theoretical calculations demonstrated that the oxygen doping could continuously modulate the band gap (from ∼2.65 eV to ∼1.32 eV), resulting in the formation of an intramolecular electron acceptor system which enhances charge separation/migration kinetics. The optimized sample exhibited remarkable photocatalytic H2 and H2O2 production rates of ∼144.8 μmol/h and ∼539.76 μM/h, respectively, which are higher than those for currently available g-C3N4-based photocatalysts. Significantly, the sample exhibited H2 and H2O2 photocatalytic yields ∼37.3 and ∼30.1 times those of pristine g-C3N4 under long-wavelength excitation (λ = 520 nm). This study developed an effective and scalable strategy for the design and synthesis of full-spectrum photocatalysts for a broad range of applications.