Localized Alkaline Microenvironments Enhanced upon Tip Effects for Efficient Antibacterial Applications

The electrochemical disinfection mechanism primarily relies on a high-voltage pulsed electric field and electrocatalytic generation of highly oxidative radicals but suffers from shortcomings of either high voltages (dozens of kV) or significant gas supply. This study proposes an in situ electrocatalytic sterilization strategy that forms localized alkaline microenvironments in neutral electrolytes under a constant current of -12 mA at a relatively lower voltage (-0.5 V vs. RHE). The nanowire cathode surface can effectively adsorb hydronium ions (H₃O⁺) from the solution during H₂ evolution, leading to a rapid increase in hydroxide ions (OH^-) concentration in the surrounding solution. This leads to a high diffusion zone of OH^-, creating a localized alkaline microenvironment. Scanning electrochemical microscopy (SECM) and finite element analysis (FEA) reveal that the nanowire-derived tip-enhanced effect significantly enhances OH^- accumulation around the cathode, effectively inactivating Escherichia coli (E. coli) at 10⁷ CFU/mL within 3 minutes at -0.5 V. The resulting increase in OH^- concentration drives rapid sterilization by inhibiting bacterial ATP synthesis and inducing oxidative stress. This method can efficiently inactivate microorganisms in a short time, while having minimal impact on the overall pH of the environment, making it a safe and environmentally friendly approach.