N,O co-doped carbon quantum dots nano-island anchored cobalt single-atom catalysts for efficient peroxymonosulfate...

The persistent contamination of aquatic ecosystems by antibiotic pollutants such as tetracycline hydrochloride (TCH) necessitates advanced oxidation processes (AOPs) for effective remediation. Peroxymonosulfate (PMS)-based AOPs offer high oxidation potential but face challenges in catalyst design, such as the conflict between catalytic activity and durability, as well as metal leaching. Herein, we developed a novel single-atom nano-island (SANI) catalyst composed of cobalt single atoms anchored on N,O co-doped carbon quantum dots (N,O-CQDs) nano-islands supported on g-C₃N₄, denoted as CoCCN. This configuration utilizes robust interactions between metal and support to simultaneously boost durability and facilitate PMS activation. The CoCCN catalyst achieved 98.3% TCH degradation within 40 min, with a kinetic constant (k_obs = 0.0873 min^-1) 2.66-fold higher than that of CoCN/PMS and 15.9-fold higher than CN/PMS. Mechanistic exploration uncovered that singlet oxygen (¹O₂) is the dominant reactive species responsible for pollutant degradation. Density functional theory (DFT) calculations further elucidated that the N,O-CQD nano-islands optimize charge transfer, reducing the energy barrier for ¹O₂ generation. The catalyst maintained 94.1% efficiency over ten cycles with minimal cobalt leaching, highlighting its robustness across a pH range of 3-10. This work provides a synergistic strategy to overcome activity-stability conflicts in single-atom catalysts for environmental applications.