Enhanced photocatalytic H2 evolution of ultrathin g-C3N4 nanosheets via surface shuttle redox

Graphitic carbon nitride (g-C3N4) is sprouted as an efficient and cost-effective visible-light-responsive photocatalyst for yielding hydrogen from water splitting. However, a brisk recombination of light-induced electron-hole (e(-)-h(+)) pairs in the bulk g-C3N4 effectuate poor quantum efficiency in the hydrogen evolution reaction (HER). The shuttle redox mediator manifests ample potential in accelerating photo-induced carrier segregation and in boosting charge transport in the HER. Here, we report that exploiting Ag/Ag(I) and Fe(III)/Fe(II) shuttle redox mediators, the hydrogen-evolving rate of the aforementioned g-C3N4 nanosheets can reach 3213.3 mmol g(-1) h(-1) under visible-light irradiation, which is eight times higher than that of pure g-C3N4 (404.82 mmol g(-1) h(-1)). The effective coupling between a hydrogen-evolving catalyst and appropriate shuttle redox mediators significantly improves the HER-photocatalytic performance of native g-C3N4 nanosheets. Density functional theory calculations show that the presence of Ag/Ag(I) and Fe(III)/Fe(II) shuttle redox mediators can effectively promote H atom adsorption and facilitate a H2O reduction reaction. This work envisages a new and deft approach for contriving high-performance g-C3N4-based photocatalysts for highly efficient solar-to-fuel conversion. (C) 2019 Elsevier B.V. All rights reserved.