Novel Au/TiO2 photocatalysts for hydrogen production in alcohol-water mixtures based on hydrogen titanate nanotube precursors

In this study, a series of titania nanorods with different phase compositions and surface areas were prepared by calcination of hydrogen titanate (H2Ti3O7) nanotubes at temperatures up to 1000 degrees C. Gold nanoparticles were subsequently deposited on the obtained TiNTx (x = calcination temperature) nanorod supports at loadings between 0.5 and 2.0 wt.%, and also onto a commercially available mixed-phase titania support (Degussa P25). TEM, XRF, UV-Vis, XPS and photoluminescence measurements confirmed the presence of gold nanoparticles of mean size 4-7 nm on the surface of the Au/TiNTx (x = 350-800) and Au/P25 photocatalysts, which suppressed electron-hole pair recombination in TiO2 under UV and created cathodic sites for hydrogen evolution. Hydrogen production tests were conducted on the Au/TiNTx and Au/P25 photocatalysts in various alcohol-water mixtures under UV excitation (6.5 mW cm(-2)) with no external bias applied. The impact of the gold loading and the calcination temperatures on the structural, physico-chemical and photocatalytic properties of the TiNTx nanorods was investigated, and a comparison to P25 was made. A 0.5 wt.% Au/TiNT600 photocatalyst demonstrated excellent H-2 production activity in all the alcohol-water systems, performing similarly to a 1.5 wt.% Au/P25 reference photocatalyst. For both the 0.5 wt.% Au/TiNT600 and 1.5 wt.% Au/P25 photocatalysts, H-2 production rates decreased in the order triol (glycerol) > diol (1,2-ethanediol approximate to 1,2-propanediol) > ethanol > 1-propanol. Good correlations were found between the H-2 production rates and alcohol properties such as the number of hydroxyl groups, polarity or standard oxidation potential. (C) 2015 Elsevier Inc. All rights reserved.