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

Graphite carbon nitride (g-C3N4) has caught far-ranging concern for its masses of advan-tages, 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 short-comings 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 atmo-sphere. 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 trans-ferred, which is favorable to photocatalytic efficiency. Among HCN, the HCN-3h sample has the highest H2 generation rate of 4297.9 mmol h-1 g-1, which achieves 2.3-fold higher than that of GCN (1291.7 mmol h-1 g-1). This paper brings forward a meaningful method of boosting the photocatalytic performance of photocatalysts by constructing abundant CVs.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Graphite carbon nitride (g-C3N4) has advantages such as a unique two-dimensional structure, low cost, nontoxic properties, suitable bandgap, and favorable stability. However, its photocatalytic efficiency is suboptimal due to low solar absorptivity and fast recombination of charge pairs. In this study, modified g-C3N4 materials with carbon vacancies (CVs) were obtained through calcination in a hydrogen atmosphere, resulting in higher specific surface area and more active sites. The CVs in the N-(C3) bond reduced electron density and narrowed the bandgap of the modified material, leading to improved light response capability. Under the synergy of abundant pore construction and CVs, the photo-excited charge pairs were effectively separated and transferred, resulting in a significantly higher hydrogen generation rate compared to g-C3N4. The study provides a meaningful method to enhance the photocatalytic performance of photocatalysts by constructing abundant CVs.