Activation of solid grinding-derived Au/TiO2 photocatalysts for solar H2 production from water-methanol mixtures with low alcohol content

Au/TiO2 nanocomposites are prepared by the solventless solid grinding method, which consists in mechanically mixing AuPPh3Cl and titania P25 and applying a mild heat treatment to reduce Au (I) into Au (0) nanoparticles (Au NP). Given that gold oxides are not thermally stable, both air and hydrogen can be considered for such treatment. Air however leads to much more efficient photocatalysts than hydrogen, due to a more efficient degradation of the gold complex, as shown by X-ray photoelectron spectroscopy, and a more effective Au-TiO2 interface. Amongst the investigated gold loadings, the composite containing 0.5 wt.% Au 0.5Au/TiO2[air] appears as the most active, yielding about 500 mu mol(H2) h(-1) g(-1) under simulated solar light in the presence of 1 vol.% methanol. This represents a marked improvement in terms of noble metal utilization, as compared with the 2 wt.% Au/TiO2 bench-marks. The yet highest efficiency (in terms of Au-normalized H-2 production) of 0.1Au/TiO2[air] (54 h(-1)), and the different trend observed with higher surface area titania, highlights the key role of the Au NP density in the photocatalytic process. (C) 2017 Elsevier Inc. All rights reserved.