Highly Efficient Performance and Conversion Pathway of Photocatalytic CH₃SH Oxidation on Self-Stabilized Indirect Z-Scheme g-C₃N₄/I^3–-BiOI

A self-stabilized Z-scheme porous g-C3N4/I3–-containing BiOI ultrathin nanosheets (g-C3N4/I3–-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/I3–-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/I3–-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/I3–-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/I3–-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/I3–-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.