Nitrogen vacancies modified graphitic carbon nitride: Scalable and one-step fabrication with efficient visible-light-driven hydrogen evolution

Abstract

Graphitic carbon nitride (g-C3N4) with nitrogen vacancies (CN-x) was fabricated by a straightforward one-step N2H4·H2O-assisted thermal polymerization method, avoiding high-energy consumption and complex post-treatment. 100-fold precursor amplification experiment proved that such a simple one-step method could achieve scalable synthesis. Experiment results show that nitrogen vacancies, introduced into CN-x architecture by removing N atoms in the C-containing triazine rings (CNC) (N2C) sites, cause bandgap narrowing and generate downward-shifted midgap states under the conduction band (CB) edge, which consequently extend the visible-light absorption and inhibit recombination of electrons and holes. As a result, under optimal amount of N2H4·H2O added, CN-75 shows a highest H2 evolution rate of 8171.4 μmol·h−1·g−1 and 3895.1 μmol·h−1·g−1 under λ > 420 nm and λ > 470 nm visible-light irradiation, respectively, far higher than that of pristine g-C3N4 (481.6 μmol·h−1·g−1, λ > 420 nm and 148.6 μmol·h−1·g−1, λ > 470 nm). Moreover, stability assays show that the as-prepared CN-75 possesses satisfactory light and structure stability after ten cycling runs (4 h per cycling). This work offers a simple and effective route for fabricating high-performance nitrogen vacancies modified g-C3N4 photocatalyst on a large scale.