An Effective, Point-of-Use Water Disinfection Device Using Immobilized Black TiO2 Nanotubes as an Electrocatalyst

The following study characterized titanium dioxide nanotube arrays (TNAs) annealed in air (air-TNA), nitrogen (N2-TNA) or hydrogen with a nitrogen balance (H2-TNA) for the rapid disinfection of waterborne bacteria. The H2-TNA became black after annealing due to a large concentration of oxygen vacancies, leading to a higher absorbance in the visible light region compared to the air-TNA and N2-TNA. Photoelectrochemical testing showed that the N2-TNA had the highest photocurrent response in the absence of an applied bias; however, under the application of a 6 V anodic bias, the photocurrent response of all the samples was dampened and the dark current of the H2-TNA was >= 50% higher than N2-TNA and air-TNA. The higher defect density in the H2-TNA compared to the other anodes led to the formation of more oxidizing radical species using only an applied bias. Complete inactivation of total coliform and E. Coli from natural creek water was obtained using a 50 ml/min flow reactor containing the H2-TNA after 25 s and under a +6 V potential in the absence of solar illumination. (C) The Author(s) 2016. Published by ECS.