ε-MnO2 with oxygen defect Engineering: Modulating local electron density to enhance superoxide radical generation via peroxymonosulfate activation

Developing cost-effective and environmentally friendly transition metal-based catalysts through defect engineering would significantly enhance peroxymonosulfate (PMS)-based Fenton-like reactions. However, precisely controlling the formation of superoxide radicals (•O 2 − ) to achieve efficient and selective degradation of refractory organic compounds, especially by Mn-based ones, continues to pose a substantial challenge. This study provides a facile solvent-thermal synthesis of defect-rich ε-MnO 2 for regulating generation of •O 2 − by the synergistic effect of Mn and oxygen vacancies (O V s). Characterization and DFT calculations demonstrated that the introduction of O V s on ε-MnO 2 microspheres substantially alter the local electronic structure. Dense O V s rendered the Mn sites electron-rich and increased the e g electron occupancy, thereby enhancing the generation of •O 2 − . The promoted electron donation and transfer process for PMS adsorption and dissociation contributed to the high performance of ε-MnO 2 . And it's the first time that we find the synergistic effect of Mn and O V s can effectively regulate their radical generation pathway, enabling the controlled production of •O 2 − .This study presents a novel approach to Fenton-like catalyst R&D, particularly expanding the utility of •O 2 − for refractory organics elimination. • O V introduction on ε-MnO 2 increases electron density and reduces electron delocalization at neighboring Mn sites. • O V increased e g electron occupancy on adjacent Mn sites, thereby enhancing catalytic reactivity. • •O 2 − generation is regulated by the synergy between Mn atoms and oxygen vacancies. • Mn 2 O 3 's higher electron density, mostly engaged in bonding, limits its performance.