Electron, hole and radical competition mechanism of layered porous g-C3N4 for hydrogen generation and organic pollutant degradation

Abstract

Halogen doping is an effective approach to regulate the electronic structure and improve photocatalytic properties of g-C3N4. Here, a salt-assisted approach was employed to prepare layered porous halogen-doped g-C3N4. The effects of halogen electronegativity and pore morphology were discussed. Highly electronegative F-doped g-C3N4 with smaller pore size and higher surface area displayed the enhanced absorption property on reactants. The H2 production rate decreased and the RhB degradation significantly increased with increasing the electronegativity of layered porous g-C3N4, which was significantly different from the conventional halogen-doped g-C3N4 prepared with halogenated acid and monolayer g-C3N4. The decreased H2 evolution can be ascribed to the strong adsorption property, and the strong interactions between halide ions and H+ were difficult to be disassociated. Additionally, the RhB degradation performance of halogen-doped g-C3N4 significantly increased with increasing the electronegativity. The most active species that dominated the RhB degradation of F-doped g-C3N4 are leaved holes (h+), which are totally different from that of the pristine g-C3N4 and Cl/Br-doped g-C3N4 (superoxide radicals,·O2–). This work helps us to well understand the role and importance of electronegativity and pore morphology on the H2 generation and RhB degradation properties of layered porous g-C3N4.