Insights into the photocatalysis mechanism of the novel 2D/3D Z-Scheme g-CN/SnS heterojunction photocatalysts with excellent photocatalytic performances.

A novel 2D/3D Z-scheme g-CN/SnS photocatalyst was successfully fabricated via self-assembly forming 3D flower-like SnS microspheres on the surface of the 2D g-CN nanosheets. The photocatalytic performances of the samples were systematically explored through catalytic reduction of Cr and oxidation of Bisphenol S (BPS) under the illumination of visible light, and the photocatalytic degradation pathway of BPS was also proposed based on the degradation products confirmed by GCMS. Among the as-prepared samples, 0.4-g-CN/SnS exhibited the most efficient photocatalytic performances, and the apparent quantum efficiency (QE) for the removal of Cr could achieve 30.3 %, which is 2.8 times higher than that of the SnS. The enhancing photocatalytic activities originated from the efficient interfacial charge migration and separation obtained in g-CN/SnS, which was firstly verified via the photoluminescence spectra, time-resolved photoluminescence spectra and photoelectrochemical characterizations. Importantly, the DFT calculated shows that the band distribution of the g-CN/SnS sample is staggered near the forbidden, which can facilitate the efficient interfacial charge migration and separation as well as result in the improvement of the catalytic activity. Finally, we put forward a more reasonable Z-scheme charge transfer mechanism, it was verified by analysing the results of free radical scavenging tests, EPR experiments and theoretical calculations.