Additive-free organic degradation via ROS excited from dissolved oxygen driven by cobalt single-atom catalyst

The generation of free radicals in advanced oxidation processes (AOPs) typically relies on external substances and energy, which significantly hinders their scalability and cost-effectiveness in wastewater treatment. Developing additive-free AOPs is essential for efficient and sustainable wastewater treatment. Herein, a new strategy for advanced oxidation is demonstrated, in which dissolved oxygen is directly activated to produce reactive oxygen species (ROS) without oxidants or energy input, achieved with a cobalt single-atom catalyst (Co-CAT-3). This strategy delivers remarkable degradation efficiency, exceeding the performance typically reported for conventional AOP systems. As a representative case for kinetic and reactive free radical species involved in organic degradation, a model organic compound, methylene blue, was used to evaluate degradation performance, which revealed a pseudo-first-order rate constant of 0.2916 min⁻¹ and a catalytic capacity of ∼0.61 μmol mg⁻¹. The proposed strategy also exhibited efficient catalytic activity toward structurally diverse organic pollutants, including representative antibiotics sulfamethoxazole (SMX) and tetracycline (TC), persistent drug carbamazepine (CBZ), endocrine-disrupting compound bisphenol A (BPA), azo dye methyl orange (MO), and small-molecule industrial intermediate maleic anhydride (MA), underscoring its universality and practical applicability. This work provides a new paradigm for additive- and energy-free ROS generation, thereby enabling efficient pollutant degradation.