Photoelectrochemical water splitting for hydrogen generation on highly ordered TiO2 nanotubes fabricated by using Ti as cathode

Sonication assisted anodization of titanium in a fluorinated ethylene glycol and water electrolyte using Ti itself as a cathode is investigated. The prepared anodic film has a highly ordered nanotube-array surface architecture. The resulting TiO2 nanotubes at potential 20–40 V have various diameters (30–100 nm), tube length (3–12 μm) and wall thicknesses (6–15 nm). The tube diameter and wall thickness are increased with the anodization time while the overall length of the nanotube arrays is controlled by the duration of the anodization time. In addition, apart from the anodization time, formation of nanotubes is governed by the distance and supplied voltages between the two electrodes, for a given electrolyte. The crystal structure and surface morphology of the annealed anodic films are investigated by XRD and SEM, respectively. The corresponding photoelectrochemical water splitting efficiency (PCE) was calculated under UV light. Our results show a very high PCE under UV (315–400 nm, 100 mW/cm2) irradiation. The maximum value of PCE for hydrogen generation obtained was 29% which is one of the best results reported in literature [1].