Zn-Bi Catalytic Pair Enables Selective Superoxide Radical Generation for Simultaneous Removal of Organic Pollutants and Heavy Metals.

Abstract

Manipulating exciton dissociation and charge-carrier transfer processes to selectively generate redox-capable superoxide (O₂ ^•-) for the removal of antibiotic-heavy metal-combined pollutants is challenging. To address this issue, a Zn-Bi catalytic pair with a dual d¹⁰ electronic configuration is constructed. The incorporation of Zn atoms into the lattice results in the formation of a Zn-O_v-Bi defect structure, thereby enhancing the built-in electric field by 5.1 times. This synergistically promotes exciton dissociation at oxygen vacancies and the directional migration of carriers. This strategy achieves an excellent charge mobility (3.76 ps) and selective activation of O₂ to O₂ ^•- (selectivity: 86.6%, 2.01 mmol L^-1 h^-1, an increase of 2.57 times). Owing to the unique charge separation mechanism, ZBOB performs excellently in the treatment of complex environmental pollutants, with simultaneous removal rates of ciprofloxacin and Cr(VI) reaching 0.55 and 0.41 min^-1, respectively, which are four and three times higher than those of the unmodified catalyst, respectively. The catalyst exhibits excellent cycling performance and stability for the simultaneous removal of ciprofloxacin and Cr(VI). These findings highlight the mechanisms underlying the charge transfer and selective generation of free radicals and provide valuable insights for the design of more efficient photocatalysts.