Dual-scale modified BiOBr with enhanced structural self-transformation at wide pH for bifunctional treatment of...

Hexavalent chromium (Cr(VI)) poses threat to both ecosystems and human health. Complex pollution conditions, particularly the pH levels, significantly influence the treatment process of Cr(VI). In this study, BiOBr materials were synthesized with exposed (110) facets and Bi vacancies through dual modifications at both grain and atomic scales. The modified material exhibits a unique pH-adaptive structural transformation capability, enhancing the treatment of Cr(VI) under variable pH conditions. This structural adaptability notably enhances the bifunctional utility of modified BiOBr under visible light. Specifically, under acidic conditions, the material's surface undergoes restructuring, progressively exposing the (001) facets in conjunction with the original (110) facets to form a heterojunction, thereby enhancing reduction capacity. Under neutral to alkaline conditions, visible-light induced surface defects increase the availability of CrO₄^2- ion-exchange channels, enhancing intercalation adsorption capacity. Additionally, facet and vacancy modifications improve the separation of charge carriers and expose more intercalation channels, enhance the pH adaptability and bifunctionality of modified BiOBr. Ultimately, the system demonstrates superior Cr(VI) removal efficiencies exceeding 90 % from pH 2-10. This innovative bifunctional BiOBr not only redefines the reaction mechanism in the Cr(VI) treatment system but also lays the groundwork for designing pH-adaptive catalysts aimed at environmental remediation.