Peculiar behavior of TiO₂ tubular structure for water reduction in dark and under natural light exposure

TiO₂ tubes were formed by electrochemical anodization process. The electrochemical reduction of water on TiO₂ tubular structure (TiO₂–TS) at various pH in dark and natural light was investigated by potentiodynamic cathodic polarization, cyclic voltammetry (CV) and impedance spectroscopy analyses. The negative shift in open circuit potential, relatively low Tafel slope and higher exchange current density presented by TiO₂–TS under natural light depicted increased electrochemical activity for water reduction. Under light exposure, CV scan showed high cathodic current density with lower overpotential (0.3 V) when compared to dark (>0.8 V). Furthermore, under natural light, the decrease in charge transfer resistance and oxide film resistance also validated the increase in the electrochemical activity of TiO₂–TS towards water dissociation.