Prompting direct single electron transfer to produce non-radical 1O2/H* by electro-activating peroxydisulfate process with core-shell cathode

A novel heteroatomic N, P and S co-doped core-shell material (MnFe 3 O 4 @PZS) was synthesized by a simple polycondensation hydro-thermal method, and used as the cathode to cooperate with electron-catalysis to activate persulfate (S 2 O 8 2− ) (E-MnFe 3 O 4 @PZS-PDS) for tetracycline (TTC) degradation. Radical scavenger studies demonstrated that non-radicals including atomic H* and singlet oxygen ( 1 O 2 ) rather than sulfate and hydroxyl radicals were the crucial reactive oxygen species (ROS). Electrochemical analysis indicated that Mn doping could promote electro-catalytic process via diverting pathway from four/two-electron to one-electron to generate non-radical H*/ 1 O 2 at the cathode, including one-electron oxygen reduction reaction (1e-ORR) ( O 2 → 1 O 2 ), and one-electron hydrogen reduction reaction (1e-HRR) ( H 2 O + e − → H ∗ ) , as evidenced by the lowest onset potential (0.072 V) together with electron transfer number (n = 1.65). Besides, the regeneration/reduction of Fe Ⅱ/Ⅲ /Mn Ⅱ/Ⅲ/Ⅳ and persulfate will not cause excessive consumption of electron and chemicals due to that could directly get the electron individually from the cathode and anode , and finally TTC could be completely degraded with low energy consumption (0.655 kWh m −3 ). This study provides new insights into the direct single electron activating PDS to produce non-radical H*/ 1 O 2 via core-shell catalytic MnFe 3 O 4 @PZS, and displays a promising application in wastewater treatment .