Rich carbon vacancies facilitated solar light-driven photocatalytic hydrogen generation over g-C3N4 treated in H2 atmosphere

Abstract

Graphite carbon nitride (g-C3N4) has caught far-ranging concern for its masses of advantages, for instance, the unique graphite-like two-dimensional lamellar structure, low cost, nontoxic, suitable bandgap of 2.7 eV and favorable stability. Whereas owing to the shortcomings of low solar absorptivity and fast recombination of photo-induced charge pairs, the overall quantum efficiency of photocatalysis for g-C3N4 is suboptimal, resulting in limited practicality of g-C3N4 (GCN). In our study, modified g-C3N4 materials (HCN) with ample carbon vacancies (CVs) were obtained through calcinating of g-C3N4 in H2 atmosphere. Higher specific surface area and more active sites of HCN were induced by roasting of g-C3N4 in H2. CVs that occurred in the N-(C3) bond lead to the reduction of electron density around N, thus narrowing the bandgap of HCN-3h and enlarging corresponding light response capability. Under the synergistic function of abundant pore construction and CVs on HCN, the photo-excited e−/h+ pairs can be memorably separated and transferred, which is favorable to photocatalytic efficiency. Among HCN, the HCN-3h sample has the highest H2 generation rate of 4297.9 μmol h−1 g−1, which achieves 2.3-fold higher than that of GCN (1291.7 μmol h−1 g−1). This paper brings forward a meaningful method of boosting the photocatalytic performance of photocatalysts by constructing abundant CVs.