Efficient peroxodisulfate activation by iodine vacancy rich bismuth oxyiodide: A vacancy induced mechanism

[Display omitted] •Iodine vacancy rich Bi7O9I3 is effective for peroxydisulfate (PDS) activation.•The Bi7O9I3/PDS system selectively oxidizes aromatic compounds.•Iodine vacancies boost electron transfer capacity and lower the Bi valence.•Bi7O9I3 activate persulfate via non-radical electron transfer mechanisms. Defect engineering is a promising strategy to improve the efficiency of persulfate based advanced oxidation processes. Different from previous reports on oxygen vacancy containing catalysts, an iodine vacancy rich material is found highly active in persulfate activation and organic degradation. The Bi7O9I3 with abundant iodine vacancies is synthesized by solvothermal method, and exhibits superior catalytic performance for peroxydisulfate (PDS) activation, with 90% phenol degradation in 60 min. Furthermore, the catalytic activity of Bi7O9I3 can be enhanced by increasing iodine vacancies through calcination below the phase transition temperature or reduction of the iodine dosage in the source materials. The electron paramagnetic resonance spectra, electrochemical measurements, and quenching tests suggest that PDS activation by the iodine vacancy rich Bi7O9I3 is a non-radical pathway. Moreover, the presence of iodine vacancies can not only increase the carrier density to boost the electron transfer capacity of the catalysts, but also lower the Bi valence to enable its role in donating electrons to PDS and receiving electrons from organic substrates. This study provides a new iodine vacancy engineered strategy for PDS activation and non-radical oxidation, and brings insights for defects induced active sites both in materials and vacancy types.