Effective Electrochemical Sterilization Based on Electrocatalysis of Oxygen Reduction by Multiwalled Carbon Nanotubes

Disinfection of drinking water is crucial for protecting the public from disease. It is therefore important to develop high-efficiency, low-cost and byproduct-free technology for the effective deactivation of organisms or pathogens in water. A study on electrochemical disinfection based on the oxygen reduction reaction (ORR) catalyzed by multiwalled carbon nanotubes (MWCNTs) is reported. MWCNTs demonstrated higher activity and comparable selectivity compared with carbon blacks toward two-electron ORR with the formation of hydrogen peroxide. By optimizing the operating conditions (pH 7.0, 50 mmol L⁻¹ phosphate buffer concentration, current density 15 mA cm⁻²), a sterilization efficiency of 99.9 % toward E. coli is achieved following electrolysis for 15 min. The oxidative species attack the cell wall of E. coli, leading to the bursting of the cell membrane and the isolation of intracellular components. Based on electrochemical disinfection driven by two-electron ORR on MWCNTs, microorganisms are removed with an efficiency of 99.9 % from the effluent of secondary clarification from a municipal wastewater treatment plant. Owing to lower energy consumption for the ORR at lower potential, this study provides a proof-of-concept demonstration of a more effective method for disinfection.