Enhanced Photoelectrochemical Generation of Hydrogen from Water by 2,6-Dihydroxyantraquinone-Functionalized Titanium Dioxide Nanotubes

Titanium dioxide, TiO2, nanotubes prepared by sonoelectrochemical anodization method are functionalized with 2,6-dihydroxyantraquinone (anthrafavic acid). The functionalization takes place by chemical condensation of the Ti−OH hydroxyl groups present on the TiO2 nanotubular surface with the phenolic hydroxyl groups of anthrafavic acid forming an inorganic−organic hybrid material. The condensation results in an intramolecular ligand-to-metal charge-transfer transition that leads to an enhancement in absorption, and an absorption band is observed in the visible region. This hybridization is responsible for an increase in the photoelectrochemical generation of hydrogen from water up to 30%.