Local microenvironment regulation with co nanoparticles/ single-atoms sites to drive two-electron oxygen reduction catalysis for efficient adsorption-electroperoxone water purification

Overcoming the inherent trade-off between pollutant adsorption and catalytic site utilization remains a critical challenge in electrochemical advanced oxidation processes (EAOPs). Herein, we develop a "Zn-evaporation induced topological reconstruction" strategy to construct a hierarchically porous carbon catalyst (MOF-5-Co-C) that features coexisting Co single-atom sites (Co-O₄) and Co nanoparticles, along with exceptional pore uniformity. The intrinsic interplay among Co single atoms, Co nanoparticles, and the hierarchical pore architecture confers a high H₂O₂ selectivity of 92.3% and a Faradaic efficiency of 86.6% for the two-electron oxygen reduction reaction (2e⁻ ORR). Through active-site poisoning experiments, impedance-based diffusion layer modeling, in situ electrochemical differential mass spectrometry, and approximate kinetic models, Co-O₄ was identified as the reactive site, the oxygen diffusion layer was quantified (7.3 μm, equivalent to 52.1% of that of the pristine MOF-5-C material), and surface reactions were revealed to dominate pollutant removal. Notably, by integrating this cathode with the electro-peroxone process, we establish a localized reaction microenvironment that enables surface reaction-mediated degradation of highly adsorbed pharmaceuticals, thereby effectively mitigating active-site masking. The developed cathode achieves over 80% total organic carbon (TOC) removal for carbamazepine in surface water with low electric energy consumption at 0.21 kWh•g^–1 TOC (5.2 kWh•m^–3), and maintains stable performance in carbamazepine removal over 100 h of operation. These results demonstrate its practical applicability for decentralized remediation of pharmaceutical-contaminated water.