Biomass derived S, N self-doped catalytic Janus cathode for flow-through metal-free electrochemical advanced oxidation process: Better removal efficiency and lower energy consumption under neutral conditions

Facing low treatment efficiency, narrow adaptive pH and high energy consumption in electro-Fenton (EF), we proposed a novel flow-through metal-free electrochemical advanced oxidation processes (EAOPs) using biomass derived S, N self-doped catalytic Janus cathode named SNJC. The SNJC was composed of a hydrophobic gas diffusion layer in the middle and hydrophilic catalytic membrane at both ends, while the catalytic membrane of S, N self-doped biomass carbon named SN-BC was derived from waste ginkgo leaves without additional supporting templates or activation processes. The conversion of graphite N, pyridinic N and thiophene S in SN-BC played a significant role in efficient oxygen reduction reaction (ORR) for H2O2 generation and in-situ active species generation. The efficient enrichment and rapid degradation of pollutants in catalytic membrane achieved almost complete removal of tetracycline within 120 min with a low energy consumption of 16.8 kWh/kg TOC. This flow-through system exhibited superior catalytic performance in wide pH ranges (3-11) due to the collective effect of radicals ((OH)-O-center dot and O-2(center dot-)) and non-radical (O-1(2)). This work provides a new insight towards the design of S, N self-doped Janus electrode and activation mechanism of in-situ generation and metal-free catalysis of H2O2 in flow-through EAOPs.