Performance comparison of Ni/TiO2 and Au/TiO2 photocatalysts for H-2 production in different alcohol-water mixtures

This study systematically compares the performance of 0.5 wt% Ni/P25 TiO2 and 2 wt% Au/P25 TiO2 photocatalysts for H-2 production in alcohol-water mixtures under UV excitation. HRTEM, XANES and EXAFS confirmed the presence of 5-8 nm Ni-0 and Au-0 nanoparticles on the surface of the photocatalysts. H-2 production tests were conducted in various alcohol-water systems (0-100 vol%), using methanol, ethanol, ethylene glycol and glycerol. The Ni/P25 TiO2 and Au/P25 TiO2 photocatalysts demonstrated remarkably similar performance for hydrogen production in all the alcohol-water systems tested. At low alcohol concentrations (15 vol% or less), H-2 production rates followed the order glycerol > ethylene glycol > methanol > ethanol, whilst at higher alcohol concentrations methanol (optimum 40 vol%) and ethanol (optimum 80-90 vol%) afforded the highest rates. Rates depended on the polarity and oxidation potential of the alcohol. Further, anatase-rutile heterojunctions in P25 TiO2 were found to greatly enhance H-2 production. (C) 2018 Elsevier Inc. All rights reserved.