Selective Electrocatalytic Reduction of Oxygen to Hydroxyl Radicals via a Three-Electron Pathway for Removing Pollutants

The traditional electro-Fenton (EF) process is limited by the generation and activation of hydrogen peroxide (H2O2). The electrochemical three-electron oxygen reduction reaction (3e– ORR) could directly activate molecular oxygen to form hydroxyl radicals (•OH), which opens up a path for the development of ecofriendly water treatment technologies. However, the main limitation of the 3e– ORR reaction at present is the lack of low-cost and high-selectivity catalytic current collectors. Herein, through coupling the 2e– active Ni sites with the common Fe and Mn sites in the Fenton reaction, the amorphous NiFeMn alloy catalytic film (A-NFM) was successfully deposited onto the current collector via a high-efficiency, reproducible, and self-developed filtering cathode vacuum arc (FCVA) codeposition system. The A-NFM could successfully selectively reduce O2 to •OH through the 3e– pathway, thereby avoiding the generation and activation of H2O2 in the Fenton process. The A-NFM can rapidly and completely remove ciprofloxacin within 30 min, achieving an apparent rate constant of 0.132 min–1, which is comparable to the most advanced oxidation processes currently available. Moreover, after 100 cycles, the degradation efficiency remains stable, indicating that this system has good stability in practical applications. This strategy can efficiently generate in situ •OH, opening up a path for the development of green water treatment technologies.