Boosting interface electron transfer between PMS and Mg-doped CoFe spinel nanocrystals for robust Fenton-like catalysis: Mechanism and toxicity analysis

Advanced oxidation processes are regarded as one of the most promising technologies for water remediation, particularly the degradation of refractory contaminants. In this study, novel cobalt-based ternary spinel nanocrystals (CMFO) were designed and synthesized using a rapid solid-phase grinding coupled with temperature-controlled pyrolysis strategy. Interestingly, the in-situ incorporation of Mg atoms into cobalt ferrite nanocrystals promoted the formation of oxygen vacancies (O v ), which in turn induced rearrangement in the local electronic structure. This change also helped to optimize the d-band center position of the catalyst, ultimately directly enhancing its capability for PMS adsorption and contaminants degradation. The optimized CMFO-5 catalyst demonstrates superior catalytic activity in the oxidative degradation of tetracycline (TC), achieving a rate constant of 0.354 min -1 , surpassing the majority of previously reported non-precious metal catalysts. Furthermore, CMFO-5 maintains >95% efficiency in the continuous degradation of TC for at least 600 min with negligible metal leaching, displaying remarkable stability. Combined structural characterization and DFT simulations confirmed the key role of Oᵥ and Mg atoms in regulating the d-band center of Co sites, thereby promoting the redox cycling of Co 2+ /Co 3+ pairs. Additionally, the unique monodispersed nanocrystals also facilitate the adsorption and electron transfer between PMS and the Co sites, contributing to the generation of abundant oxygen radicals. This work provides a case study on structural and electronic regulation in spinel oxides, which could be expanded to the synthesis of other advanced metal catalysts for water remediation. The rational optimization of d-band center in Mg-doped CoFe 2 O 4 nanocrystals promotes the redox cycling of Co 2+ /Co 3+ pairs and facilitates the activation and electron transfer between PMS and Co sites, thus demonstrating exceptional performance for degradation of refractory pollutants under mild conditions. • Oᵥ-rich cobalt ferrites was synthesized via a doping engineering strategy. • Enhanced charge transfer capability was achieved on the optimized MCFO. • 92.6% tetracycline degradation was achieved in 7 min in Fenton-like process. • CMFO maintains >95% TC sustainable degradation for at least 600 min. • Oᵥ and Mg doping synergy enhance PMS activation and radicals generation.