Enhanced H2O2 production via S doped N-rich biochar natural air diffusion electrode in an electro-Fenton system for efficient tetracycline degradation

Electro-Fenton (EF) technique is recognized as one of efficient advanced oxidation technologies for degrading recalcitrant biological pollutants. However, the practical application of EF technique suffers from poor 2e − oxygen reduction reaction (ORR) selectivity and low H 2 O 2 production efficiency. To settle above-mentioned issues, a natural air diffusion electrode (NADE)-EF system was constructed by using S doped N-rich biochar as a cathode, which was synthesized from waste mantis shrimp shells and thiourea. By modulating the biochar/thiourea ratio, the S doped N-rich biochar cathode achieved selective 2e − ORR and highly efficient H 2 O 2 production. The production rate of H 2 O 2 on the S doped N-rich biochar cathode was 1.56 times that on the undoped biochar cathode. The S doping enhanced the O 2 adsorption and electron transfer and facilitated the *OOH intermediate formation. The tetracycline degradation rate in the S doped N-rich biochar NADE-EF system was 2.29 times that of the undoped biochar NADE-EF system. The S doped N-rich biochar NADE-EF system showed good cyclic stability and anti-interference ability. This work provides the insights into the structure-activity relationship between heteroatom doping and H 2 O 2 production through 2e − ORR and proposes an efficient NADE-EF technique to remove antibiotics from water.