Photocatalytic performance of Au/ZnO nanocatalysts for hydrogen production from ethanol

Gold was loaded on several ZnO samples with different morphologies: needle-like (ZnO-n), flower-like (ZnO-f), rods (ZnO-r), and prepared by a thermal calcination process (ZnO-t). A commercial ZnO sample (ZnO-c) was also used for comparison. Bare ZnO and Au/ZnO materials were used for the photocatalytic production of H-2 from a water-ethanol solution under UV-vis irradiation (lambda > 300 nm). During the photocatalytic runs, hydrogen was generated at a constant rate for all samples, as well as CH4 and CO. The obtained results show that bare ZnO materials were able to promote H-2 photogeneration, being ZnO-f the most efficient in terms of H-2 generation. Loading with Au, in general, increased the photoefficiency for all materials. The most active gold loaded photocatalysts were the ones with the lowest gold nanoparticle sizes: Au/ZnO-f (427 mu mol h(-1) g(cat)(-1); 5.4 nm) and AugnO-n (280 mu mol h(-1) g(cat)(-1); 5.8 nm). The samples with largest size (Au/ZnO-r and AulZnO-t with 6.2 nm, and Au/ZnO-c with 12.5 nm) were not so efficient (values below 230 mu mol h(-1) g(cat)(-1)). Au/ZnO-f seems to be the most promising photocatalyst, generating the highest amount of H-2 and the lowest quantities of CH4 and CO. It is also possible that the intricate morphology of ZnO-f may scatter the incoming light, enhancing light absorption efficiency and increasing the photoefficiency of this material. (C) 2015 Elsevier B.V. All rights reserved.