Modulating mesoporous Co₃O₄ hollow nanospheres with oxygen vacancies for highly efficient peroxymonosulfate activation

The role of oxygen vacancy (V_O) in catalyst is manifested to be positive in the Fenton-like process. However, rational modulation of V_O with a simple strategy for the efficient Fenton-like catalysts remains desirable and challenging. Here a facile heat treatment method without any additives was demonstrated to introduce V_O on mesoporous cobalt oxide (Co₃O₄) hollow nanospheres, which served as highly reactive and stable Fenton-like catalysts for recalcitrant organic pollutants (bisphenol A, BPA) degradation by activating peroxymonosulfate (PMS). The V_O-rich Co₃O₄ nanospheres exhibited superior BPA removal efficiency with high BPA degradation rate (0.0232 min⁻¹, 100 min). The concentration of V_O in Co₃O₄ was proved to act as an important role for the PMS activating efficiency. A series of mechanism studies, including radical scavengers, chemical probes and electrochemical characterizations, were conducted to identify the active radicals generated by PMS activation. Singlet oxygen produced from the V_O-based reaction pathway, rather than sulfate radical and hydroxyl radical, was unveiled to play a key role in the BPA degradation process. This work provided new insight into designing transition metal oxide-based Fenton-like catalysts with efficient and sustainable remediation of refractory organic contaminants in wastewater.