Gold nanoparticle decorated ceria nanotubes with significantly high catalytic activity for the reduction of nitrophenol and mechanism study

We report the preparation and catalytic properties of a new nanostructured catalyst, made of small (similar to 5 nm in diameter) and uniform gold nanoparticles (AuNPs) and ceria nanotubes (CeO2 NTs). "Surfactant-free" AuNPs fabricated by pulsed laser ablation in liquid (PLAL) on a bulk Au target are efficiently assembled onto the surface of CeO2 NTs without performing any surface functionalization of either component to promote their coupling, thanks to the presence of -OH on the PLAL-AuNPs. The reduction reaction of 4-nitrophenol into 4-aminophenol catalyzed by our PLAL-AuNP/CeO2-NT catalyst exhibits remarkably higher reaction rate in comparison to that catalyzed by similar catalysts composed of chemically prepared AuNPs (Chem-AuNPs) as an active phase and/or commercially available CeO2 powder as support. Their superior catalytic activity is found to be due to the unique, relatively "bare" surface of the PLAL-AuNPs as well as oxidized Au species induced by the strong interaction between the "barrier-free" surface of PLAL-AuNPs and surface defects (oxygen vacancies) of CeO2 NTs. The important role of unique surface chemistry of PLAL-AuNPs in catalysis was further demonstrated in CO oxidation reaction in gas phase. Our results suggest that the use of PLAL-AuNPs enables easy and efficient attachment of AuNPs onto the surface of the CeO2 NTs and their unique combination leads to the development of highly efficient catalysts. Our design and fabrication of the nanocatalysts take full advantage of the unique features of the PLAL-AuNPs and potentially constitute a general and efficient route to prepare other metal-NP/metal-oxide-support catalysts, which can therefore largely expand the applications of PLAL-noble metal NPs in catalysis. (C) 2012 Elsevier B.V. All rights reserved.