In situ fabrication of ultrathin-g-C3N4/AgI heterojunctions with improved catalytic performance for photodegrading rhodamine B solution

• Ultrathin-g-C 3 N 4 /AgI heterojunction photocatalysts were designed and prepared simply. • Coordination adsorption and in-situ growth yield a high-quality heterojunction interface. • The heterojunction photocatalysts exhibited superior catalytic activity. • A type II charge transfer pathway of the heterojunction photocatalysts is proposed. Heterojunction photocatalysts with controllable compositions and textures have attracted extensive research interest in environmental pollutants degradation owing to the superior catalytic activity compared to their single component counterparts. Herein, a series of ultrathin-g-C 3 N 4 /AgI heterojunctions (UCNA) were prepared by ultrasonication-assisted liquid exfoliation of bulk g-C 3 N 4 followed by characteristic inner-sphere surface complexation of Ag (I) and in-situ growth of AgI on ultrathin g-C 3 N 4 nanosheets. The structural features and optical properties of all the prepared samples were investigated using X-ray powder diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffused reflectance spectroscopy (UV–vis DRS) and photoluminescence spectroscopy (PL) prior performing photocatalytic activity. The as-prepared heterojunctions showed significant improvement in photocatalytic activity in comparison with pure AgI and g-C 3 N 4 nanosheets with the complete degradation of rhodamine B (RhB) in 60 min at UCNA-70% sample under visible light irradiation with good recycling characteristics. The superior photocatalytic performance of the heterojunctions can be attributed to the combined effects of tightly coupled high-quality interface, appropriate energy band structure and position, along with the increased charge separation and migration efficiency. Based on the analysis of interfacial charge-transfer process across the ultrathin-g-C 3 N 4 /AgI heterojunction, a plausible photocatalytic mechanism of ultrathin-g-C 3 N 4 /AgI composites was presented.