Novel Three-Dimensional Electrochemical Reactor with P and N-Codoped Activated Carbon for Water Decontamination: High Efficiency and Contribution of Singlet Oxygen

A three-dimensional (3D) electrolysis cell with P and N-codoped carbon materials (PCN) utilized as particle electrodes was fabricated for efficient water decontamination by singlet oxygen (1O2) without the addition of oxidants as precursors. The results showed that the degradation of sulfamethoxazole (SMX) during 3D electrolysis was 7.68 times faster than that during conventional two-dimensional (2D) electrolysis, while the energy consumption in the 3D mode was only 0.37 of the latter. The rapid degradation of SMX primarily resulted from the generated reactive oxygen species (ROS) in the 3D mode. Electron spin resonance (ESR) techniques and scavenging experiments indicate that 1O2 rather than radical species contributed to SMX degradation. 1O2 was generated via a series of superoxide-mediated chain processes, which was initiated by the oxygen reduction reaction (ORR) on the cathode and subsequently terminated by H2O2 oxidation on the anode and PCN. SMX degradation in the 3D mode was nearly unaffected by the water matrices, and a high efficiency in synthetic fresh urine and simulated hospital wastewater was maintained. Furthermore, PCN exhibited high structural stability and reactivity after five cycles. Hence, this work provides a promising strategy to generate 1O2 for contaminant degradation during water treatment.