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

A novel heteroatomic N, P and S co-doped core-shell material (MnFe₃O₄@PZS) was synthesized by a simple polycondensation hydro-thermal method, and used as the cathode to cooperate with electron-catalysis to activate persulfate (S₂O₈^2-) (E-MnFe₃O₄@PZS-PDS) for tetracycline (TTC) degradation. Radical scavenger studies demonstrated that non-radicals including atomic H* and singlet oxygen (¹O₂) 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*/¹O₂ at the cathode, including one-electron oxygen reduction reaction (1e-ORR) (O₂→¹O₂), and one-electron hydrogen reduction reaction (1e-HRR) (H₂O+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*/¹O₂ via core-shell catalytic MnFe₃O₄@PZS, and displays a promising application in wastewater treatment.