Modulating covalency competition and neutral microenvironment in cobalt spinel catalysts enables sustainable peracetic acid activation and ultrafast antibiotics degradation

Conventional cobalt spinel oxides, widely employed in advanced oxidation processes, suffer from limited catalytic activity due to competitive overlap of O 2p orbitals between tetrahedral (Co_Td) and octahedral cobalt (Co_Oh). Furthermore, their narrow pH activity window near neutrality severely restricts environmental applicability. To address these limits, the theories of covalency competition and microenvironment modulation are introduced to simulate the catalytic process and propose optimization strategies. By incorporating less electronegative zinc into tetrahedral sites, the covalency competition within the Co_Td−O−Co_Oh backbone was modulated, reversing the unfavorable Co_Oh−O covalency. The synthesized Zn-Co-O exhibits more delocalized electrons and a reduced activation energy barrier towards peracetic acid activation, increasing the reaction rate for sulfamethoxazole removal by 43.6 folds. Additionally, the amphoteric nature of Zn constructs a neutral microenvironment around Co_Oh, maintaining excellent catalytic performance across a broad pH range (3.0 − 9.0), with Co^IV=O and RO^• identified as the primary reactive oxygen species under acidic and neutral conditions, respectively. The innovative guideline for the rational design of spinel catalysts demonstrates broad application prospects in sustainable contaminated water remediation.