Enhanced light-driven photoelectrochemical catalysis of water splitting by TiO₂ nanotubes grown on acid-etched titanium foils

Titanium dioxide with suitable band edges is one of promising photocatalysts for water splitting. Nanotubes with one-dimensional structure can induce efficient charge transfers and hollow centers can provide large surface area for surface reactions. Modifying Ti foils for anodization can enhance light utilization of TiO₂ nanotube photoelectrodes. In this work, it is firstly to fabricate TiO₂ nanotube photoelectrodes on acid-etched Ti foils by anodization (MNT) for photoelectrochemical catalyzing water splitting. Different acid-etching durations are applied on Ti foils to induce various rugged surfaces. The resulting photoelectrodes present largely enhanced light utilization than that fabricated by the pristine Ti foil. The anodization duration is also optimized to find suitable lengths of MNT. The smallest overpotential of 524.7 mV at 10 mA/cm² and Tafel slope of 167 mV/dec are obtained for the optimal MNT photoelectrode. The TiO₂ nanotubes grown on the pristine Ti foil shows the overpotential of 679.3 mV at 10 mA/cm² and Tafel slope of 285 mV/dec. This result opens a blueprint for raising the photocatalytic ability by simply modifying the surface property of the conductive substrate. Other modifications may be applicable to enhance the roughness of Ti foils for growing more efficient MNT array as photocatalysis of water splitting.