TiO2–g-C3N4–BiOI nanoflower heterojunction for boosting photocatalytic methyl orange degradation

A novel TiO 2 –g-C 3 N 4 –BiOI (TCB) dual-heterojunction nanocomposite with a hierarchical nanoflower morphology was synthesized via a combined hydrothermal–calcination method. The TCB-2 sample, which contained 2.4% Bi, exhibited exceptional photocatalytic activity for methyl orange degradation, achieving 98.55% removal under xenon-lamp irradiation within 100 min. SEM characterization revealed a nanoflower architecture composed of interlaced nanosheets with abundant interspaces, providing increased active sites and facilitating reactant diffusion. UV–Vis DRS analysis confirmed the narrowed optical band gap and extended visible-light absorption range. The formation of intimate contact between components, which is a prerequisite for heterojunctions, was supported by XRD and XPS analyses, suggesting the possible establishment of dual heterojunctions (Type II and p-n). The catalyst maintained an 82.80% degradation efficiency after three cycles, demonstrating excellent stability. This work provides valuable insights for designing TiO 2 -based photocatalysts with enhanced visible-light utilization for environmental applications.