A sustainable production of H2 by water splitting and photo-reforming of organic wastes on Au/TiO2 nanotube arrays

We report here on the sustainable production of hydrogen by the use of nano-ordered TiO2 arrays doped with gold nanoparticles (Au NPs). The presence of a nano-architecture in TiO2 substrate may strongly improve the ability to disperse the Au NPs on its surface, which act as electron-attractive centres for the reduction of protons. We prepared the TiO2 nanotube arrays by controlled anodic oxidation starting from Ti foils and deposited the Au NPs by pre-preparing gold colloidal solutions. The samples were characterized by Transmission Electron Microscopy (TEM), UV-Visible Diffusive Reflectance Spectroscopy, Cyclic Voltammetry and Chronoamperometry. Then, they were tested within our homemade photo-electrochemical (PEC) reactors in water photo-splitting, as well as in photo-dehydrogenation of ethanol for H2 production. A solar simulator was used to evaluate their photo-responses in different absorption regions (ultraviolet or visible part). Results evidenced that smaller Au NPs strongly enhanced titania performances under visible light irradiation, opening the route of a feasible implementation of the PEC devices in the energy recovery from organic waste solutions (i.e. from biomass processing) that are too dilute to be processed by conventional routes.