Spin-state modulation boosts *OOH intermediate generation for Ni-Co3O4 catalyst in electro-Fenton like process

The electronic structure of metal oxides plays an important role in determining their catalytic activity, but how to regulate this structure to overcome inherent limitations in electron transfer efficiency and spin state configuration remains a significant challenge. Herein, we designed a Ni-doped Co 3 O 4 nanorod, where Ni occupied at the octahedral site can effectively facilitate the spin-state transition of Co 3+ from a low-spin to a high-spin state, inducing an electronic structure reconstruction in Co 3 O 4 . This not only increases the e g filling of Co 3+ but also generates additional electronic states, benefiting water purification process. As expected, the obtained Ni-Co 3 O 4 -4 catalyst exhibits excellent catalytic performance in electro-Fenton like (EF-like) system, achieving a ciprofloxacin (CIP) removal efficiency of 94.3%, with a rate constant ( k ) 1.69 times higher than that of Co 3 O 4 . In situ Raman spectra confirmed that the charge rearrangement between Ni and Co 3 O 4 facilitated the formation of the key *OOH intermediate, promoting the production of superoxide radicals (·O 2 - ). Additionally, the developed Ni-Co 3 O 4 -4 system can operate continuously for 600 min in a continuous-flow reactor. This work deepens the comprehensive understanding of the relationship between electrocatalytic activity and the spin configuration of Co ions, offering an effective design strategy for spinel compound catalysts aimed at environmental remediation.