Ov-rich γ-MnO2 enhanced electrocatalytic three-electron oxygen reduction to hydroxyl radicals for sterilization in neutral media.

Marine biofouling severely limits the development of the marine economy, and reactive oxygen species (ROS) produced by electrocatalytic antifouling techniques could inactivate marine microorganisms and inhibit the formation of marine biofouling. Compared with an electro-Fenton reaction, a three-electron oxygen reduction reaction (3e- ORR) could generate a hydroxyl radical (˙OH) in situ without the limitation of pH and iron mud pollutants. Herein, Ov-rich γ-MnO2 is designed to enhance the 3e- ORR performance in neutral media and exhibits excellent sterilization performance for typical marine bacteria. DFT calculation reveals that Ov is beneficial to the "end-on" adsorption and activation of O2, and the Mn site could accept the electrons from *OOH and promote its further reduction to form ˙OH; Ov and Mn sites together guarantee the high 3e- ORR efficiency. In addition, liquid chromatography-tandem mass spectrometry (LC-MS/MS) proves the vast formation of ˙OH in the primary reaction stage, which is the key to sterilization. This work explores the reaction mechanism of the 3e- ORR in neutral media and provides the possibility for the application of electrocatalysis technology in the treatment of marine biofouling pollution.