Enhancing photocatalytic degradation of rhodamine B with visible-light-driven HCl-assisted Bi2O3 photocatalysts: Activity, mechanism, and pathways

This study utilized X-diffraction, BET, photoluminescence , UV–vis DRS, FTIR , SEM, XPS , TOC analysis, EPR , electrochemical measurements, and LC-MS to characterize the structural characteristics, morphology, optical properties , photocatalytic activity , surface electronic states, active compounds, and potential photodegradation pathways of rhodamine B (RhB) over as-prepared Bi 2 O 3. The as-prepared Bi 2 O 3 photocatalyst exhibited a narrow bandgap, which enabled efficient absorption of visible light, thereby contributing to its enhanced photocatalytic activity. Additionally, Bi 2 O 3 exhibited a high degradation efficiency for RhB. with up to 96.8 % of RhB removed within 120 min at pH 3.0. The excellent photocatalytic performance of Bi 2 O 3 can be attributed to the formation of the heterogeneous Bi 2 O 3 /BiOCl structure on the Bi 2 O 3 surface in the presence of HCl. Moreover, the TOC analysis revealed that over 58.1 % of the carbon in the RhB solution was mineralized into CO 2 after 120 min of irradiation. The effect of catalyst content, RhB concentration, initial pH, and inorganic anions on the photocatalytic degradation of RhB over Bi 2 O 3 was examined. Furthermore, the active compounds and potential photocatalytic mechanism of the Bi 2 O 3 /BiOCl heterogeneous structure toward RhB were evaluated. The intermediates formed during RhB degradation were identified, and the corresponding degradation pathway was deduced via LC-MS.