Oxygen-vacancy-mediated BrO3− electroreduction: Positively charged microenvironment enables directional diffusion and spontaneous adsorption

Journal article, 2026

Ozonation can disinfect drinking water without producing chlorinated byproducts, but BrO3⁻ emerges as a carcinogenic by-product. Although the electroreduction could theoretically convert BrO3⁻ into non-toxic Br⁻, the detoxification process was hindered by the electrostatic repulsion of BrO3⁻ from the negatively charged cathode. In this work, a commercial Fe foam was employed for electrochemically reducing BrO3⁻ via a direct electron transfer mechanism, during which microcrystalline magnetite (Fe3O4) was in-situ generated with abundant oxygen vacancies (Ovs). The Ovs shaped neighboring Fe²⁺ atoms into a positively charged microenvironment for accelerating the directional diffusion of BrO3⁻. Furthermore, Ovs activated the neighboring Fe²⁺ atoms into highly active sites for BrO3⁻ adsorption in comparison to the energy-demanding adsorption on intact Fe3O4. Afterwards, BrO3⁻ underwent complete detoxification with Ovs assisting throughout the whole process. By the in-situ defect engineering, the research points out an efficient approach to create a positively charged microenvironment for enhancing oxyanion electroreduction.