Atomic-Level Regulation of Oxygen Coordination in Co-N-C Catalysts for Selective Hydrogen Peroxide Production and Efficient Degradation of Tetracycline in Bio-Electro-Fenton System

The production of hydrogen peroxide via the two-electron oxygen reduction reaction has emerged as a sustainable route for electro-Fenton technology in wastewater treatment, yet it remains challenged by the competing four-electron pathway and the lack of atomic-level structure-selectivity relation explanation, especially in acidic media. Here, precisely engineered CoN 3 O 1 atom sites are constructed by substituting an N atom with an O atom in CoN 4 coordination, thereby realizing atomic-level regulation of the first coordination shell in Co-N-C catalyst. Density functional theory (DFT) calculations and advanced spectroscopy reveal that precise O substitution for N modulates the Co electronic structure and spin state, optimizes *OOH adsorption free energy, and inhibits O-O bond cleavage. As a result, CoN 3 O 1 delivers higher than 90% H 2 O 2 selectivity. In situ Raman and isotope-labeled differential electrochemical mass spectrometry (DEMS) capture the *OOH intermediate and further verify the 2e - pathway. In bio-electro-Fenton system, CoN 3 O 1 realizes 97.9% tetracycline removal and high mineralization efficiency without consuming external electrical energy. This work clarifies the role of atomic-level oxygen coordination engineering in governing 2e - ORR selectivity and provides a general design principle for advanced single-atom catalysts in bio-electro-Fenton systems.