Boosting peracetic acid activation with Cu single-atom catalysts for sulfamethoxazole abatement: A nonradical pathway and ‘double engine’ driving mechanism

Herein, a Cu single-atom catalyst with ultrahigh loading of Cu-pyridinic N4 sites on carbon nanosheets (CuSA-N-C) is successfully designed and synthesized as an activator for peracetic acid (PAA). The CuSA-N-C showed the most powerful capacity for PAA activation among the Cu-based catalysts, and even a 48-fold enhancement on sulfamethoxazole (SMX) degradation compared to homogeneous Cu2+. The scavenging experiments and ESR analysis indicated that singlet oxygen (1O2) but not conventional radicals play a dominant role in SMX degradation. Theoretical calculations further insights into the generation of 1O2 in PAA activation. Furthermore, a 'double engine' driving mechanism was proposed, where the electron-rich area around Cu site and the electron-poor area around C site in the saturated Cu-N4 configuration could efficiently adsorb and activate PAA. The CuSA-N-C/PAA process exhibited high tolerance towards the common water matrices (e.g., CO32−/HCO3− and Cl-), and thus showed excellent performance in the real wastewater. This study advances the understanding of non-radical PAA activation process and provides guidance for the design of smart PAA-active catalysts.