Strong electrocatalytic decoupling of persulfate and oxygen reduction using atomically dispersed NiN4 as a strategy for efficient antibiotic removal from wastewater

Carbon materials containing dispersed nickel single atoms have shown excellent activity as electrocatalysts in different areas. This study reports the first application of a catalyst with Ni–N–C moieties to cathodic persulfate (PS) activation, an innovative route that triggers the in-situ production of reactive oxygen species (ROS). The presence of NiN 4 sites was unveiled via HAADF–STEM and synchrotron analysis. Ni–SAC was employed in persulfate reduction reaction (PSRR) to electrogenerate SO 4 •– radical in oxygenated medium. A remarkable decoupling of PSRR from undesired oxygen reduction reaction (ORR) was achieved, as evidenced by the much higher onset potential of the former (i.e., ∼1.16 V|RHE vs ∼0.45 V|RHE). Great selectivity was determined for PSRR (1e − route, yielding SO 4 •– ) and ORR (4e − route, yielding H 2 O). Degradation tests showed the ability of Ni–SAC to attain the complete elimination of the antibiotic piperacillin at 20 mA cm −2 , in both model and actual water matrices. Electron paramagnetic resonance revealed that SO 4 •– rather serves as precursor of other ROS like • H, • OH and H 2 O •+ . Of note, water radical cations are detected for the first time in PS-based advanced water treatment. Overall, our observations bring about new possibilities for more efficient wastewater treatment.