Enhanced photo-Fenton degradation for amoxicillin in aqueous by halogen-facet synergistic regulation of BiOX: Insights into photogenerated electron migration and oxidant activation

Halogen selection and facet engineering were effective strategies for catalyst optimization, however, their synergistic mechanism in enhancing photo-Fenton performance remained unclear. In this study, the effects of halogens (Br and I) and facets ({001}, {010} and {110}) on the photo-Fenton degradation of amoxicillin (AMX) by BiOX were systematically investigated. The results revealed that halogen selection and facet engineering enhanced the photo-Fenton performance by improving the separation efficiency of photogenerated electron ( e − ) and their activation capability toward oxidants. Among them, halogen selection (Br) played a dominant role in enhancing the degradation performance, while facet engineering ({010} facet) contributed secondary optimization. Experimental results demonstrated that in the presence of peroxydisulfate (PDS, 0.065 mM) and hydrogen peroxide (H 2 O 2 , 0.065 mM), BiOBr exhibited superior photo-Fenton performance to BiOI on all facets. For the same halogen, the BiOX with the {010} facet (BiOX-010/vis/oxidant) outperformed BiOX-001/vis/oxidant and BiOX-110/vis/oxidant in degradation activity. Further analysis from the perspective of band structure and photoelectrochemical properties revealed that BiOBr enhanced photogenerated e − separation efficiency and reduction capacity by modulating its band structure. Work function calculations indicated that exposure of the {010} facet facilitated the migration of photogenerated e − through Br–Bi/Br–O–Bi bonds, reducing its interfacial work function (2.72 eV), thereby significantly improving interfacial charge transfer efficiency. Under this synergistic regulation strategy of halogen and facet, BiOBr-010 exhibited the strongest PDS adsorption affinity ( E ads  = 2.78 kJ/mol), enabling BiOBr-010/vis/PDS to achieve excellent AMX degradation performance ( k obs  = 0.028 min −1 ). This study elucidate the contributions and mechanisms of halogen and facet types to the photo-Fenton performance, providing design strategies for the development of efficient and stable photo-Fenton systems.