Role of the active chlorine generated in situ on the photoelectrocatalytic inactivation of bacteria and fungi with TiO2 nanotubes

Immobilised TiO2 nanotube (TiO2-NT) electrodes were grown via electrochemical anodisation in an aqueous solution containing fluoride ions at 10, 20 and 30 V. The photocatalytic (PC) and photoelectrocatalytic (PEC) activity of TiO2- NTs electrodes in the oxidation of methanol and the inactivation of bacteria and fungi was studied in different chloride salts electrolytes. Low concentrations of electrochemically generated oxidising species, such as free chlorine, were measured in experiments at pH 8.5 and +1 V of applied potential. Increasing the anodising potential results in longer nanotubes with higher photoactivity. The TiO2-NT electrode anodised at 30 V (TiO2-NT30V) generates free chlorine with an average concentration of 0.03 mg·L−1 upon illumination with UV-A at +1 V of potential bias. This concentration was enough to achieve 99.99 % of inactivation of a 106 CFU·mL−1 Gram-negative bacteria (Escherichia coli) in