Revealing the transfer mechanisms of photogenerated charge carriers over g-C3N4/ZnIn2S4 composite: A model study for photocatalytic oxidation of aromatic alcohols with visible light

Semiconductor photocatalysis as an alternative technology has received extensive attention for addressing the worldwide energy and environment issues. However, it is still a great challenge and imperative to profoundly understand the migration mechanisms for achieving the complete utilization of photoexcited charge carriers. In this paper, a series of g-C3N4/ZnIn2S4 heterojunction composites were fabricated by thermal polycondensation and solvothermal methods and then thoroughly characterized by a range of techniques. Photocatalytic selective oxidation of aromatic alcohols to corresponding aldehydes with O2 under visible light irradiation was introduced as a model reaction system to evaluate the photocatalytic performance of the as-prepared samples. The results exhibit that when the main constituent of photocatalyst is ZnIn2S4, the transfer of the photogenerated charge carriers adopts a band-band mechanism in g-C3N4/ZnIn2S4 heterojunction composite. However, when the main constituent of photocatalyst is g-C3N4, the transfer of the photogenerated charge carriers adopts a Z-scheme mechanism. Therefore, the different compositions of the composite samples lead to the different electronic conductivities and then affect the direction of the built-in electric field in the relative p-n junction, finally causing the different transfer mechanisms of the photogenerated charge carriers for g-C3N4/ZnIn2S4 composite samples.