Concave-pore defective BiOCl applied to photodegradation of Rhodamine B: mechanism, degradation pathway and toxicity analysis

Morphological engineering is utilized to modify the microstructure and electronic structure of bismuth oxychloride; this led to a remarkable enhancement in photocatalytic performance. In this research, H-BOC nanosheets with concave-pore defects were synthesized via a glycol-mediated solvothermal etching method. Photocatalytic activity was examined using Rhodamine B (RhB, 20 mg·L⁻¹) as the target contaminant under visible-light exposure. H-BOC displayed superior photocatalytic performance within 4 min, achieving a degradation rate of 99% and a reaction rate constant of 0.9643 min^–1, significantly higher than those of T-BOC (53% and 0.1556 min^–1). The results indicate that the incorporation of concave-pore defects not only improves visible-light absorption and reduces hole migration distance but also enhances charge separation and effectively suppresses the recombination of photogenerated electron–hole pairs. This acceleration in reaction kinetics was further confirmed by trapping experiments and EPR analyses, which reveal that superoxide (•O₂⁻) and hydroxyl radicals (•OH) were the dominant reactive species. Furthermore, high-performance liquid chromatography–mass spectrometry (HPLC–MS) and the toxicity estimation software tool (T.E.S.T) were employed to investigate the degradation mechanisms, pathways, and the toxicity of RhB and its intermediates. This study presents a novel approach for designing and developing high-performance photocatalysts.