Highly Efficient Performance and Conversion Pathway of Photocatalytic CH₃SH Oxidation on Self-Stabilized Indirect...

A self-stabilized Z-scheme porous g-C₃N₄/I^3--containing BiOI ultrathin nanosheets (g-C₃N₄/I^3--BiOI) heterojunction photocatalyst with I₃^-/I^- redox mediator was successfully synthesized by a facile solvothermal method coupling with light illumination. The structure and optical properties of g-C₃N₄/I^3--BiOI composites were systematically characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, X-ray photoelectron spectroscopy, N₂ adsorption/desorption, UV-vis diffuse reflectance spectrum, and photoluminescence. The g-C₃N₄/I^3--BiOI composites, with a heterojunction between porous g-C₃N₄ and BiOI ultrathin nanosheets, were first applied for the photocatalytic elimination of ppm-leveled CH₃SH under light-emitting diode visible light illumination. The g-C₃N₄/I^3--BiOI heterojunction with 10% g-C₃N₄ showed a dramatically enhanced photocatalytic activity in the removal of CH₃SH compared with pure BiOI and g-C₃N₄ due to its effective interfacial charge transfer and separation. The adsorption and photocatalytic oxidation of CH₃SH over g-C₃N₄/I^3--BiOI were deeply explored by in situ diffuse reflectance infrared Fourier transform spectroscopy, and the intermediates and conversion pathways were elucidated and compared. Furthermore, on the basis of reactive species trapping, electron spin resonance and Mott-Schottky experiments, it was revealed that the responsible reactive species for catalytic CH₃SH composition were h⁺, ^•O₂^-, and ¹O₂; thus, the g-C₃N₄/I^3--BiOI heterojunction followed an indirect all-solid state Z-scheme charge-transfer mode with self-stabilized I₃^-/I^- pairs as redox mediator, which could accelerate the separation of photogenerated charge and enhance the redox reaction power of charged carriers simultaneously.