In situ photoelectrocatalytic generation of bactericide for instant inactivation and rapid decomposition of Gram-negative bacteria

A bactericidal technique (PEC–Br) utilizing in situ photoelectrocatalytically generated photoholes (h+), long-lived di-bromide radical anions (image) and active oxygen species (AOS) for instant inactivation and rapid decomposition of Gram-negative bacteria such as Escherichia coli (E. coli) was proposed and experimentally validated. The method is capable of inactivating 99.90% and 100% of 9 × 106 CFU/mL E. coli within 0.40 s and 1.57 s, respectively. To achieve the same inactivation effect, the proposed method is 358 and 199 times faster than that of the photoelectrocatalytic method in the absence of Br−, and 2250 and 764 times faster than that of the photocatalytic method in the absence of Br−. The decomposition experimental results obtained from 600-s PEC–Br-treated samples demonstrated that over 90% of E. coli body mass was decomposed and 42% biological carbon contents in the sample was completely mineralized and converted into CO2. The mechanistic pathways of disinfection/decomposition by photocatalysis (PC), photoelectrocatalysis (PEC), and photoelectrocatalysis in presence of Br− (PEC–Br) were also illustrated based on experimental evidence.