Fabrication of a dual S-scheme BiOI/g-CN/BiOCl heterojunction with enhanced visible-light-driven performance for phenol degradation.

S-scheme heterostructure can facilitate the separation of carriers while maintain outstanding redox capacity. A series of ternary BiOI/g-CN/BiOCl photocatalytic system was triumphantly synthesized via oil bath method in this work and used in photocatalytic degradation of phenol. The optimal TOC removal rate reached up to 93.57% under illumination for 160 min, which was slightly lower than phenol photodegradation (about 100%, 100 min). Correspondingly, the apparent rate constants for the decay of phenol are determined to be 0.0211 min. The experiment of free radical capture indicated that ·OH and ·O were the major oxidizing substances to degrade phenol. The products of phenol photodegradation were identified by high performance liquid chromatography (HPLC) and a possible degradation pathway was proposed. The characterization analysis and density functional theory (DFT) calculations demonstrated that dual S-scheme charge migration was generated at the interface of BiOI, g-CN and BiOCl, contributing to an efficient separation of light-excited carriers. In the field of environmental remediation, the discovery of this work could open up promising vistas for designing bismuth-based ternary heterostructures with application potentiality.