The catalytic activity of gold depends on particle size, with the reactivity increasing as the particle diameter decreases. However, investigations into behaviour in the subnanometre regime (where gold exists as small clusters of a few atoms) began only recently with advances in synthesis and characterization techniques. Here we report an easy method to prepare isolated gold atoms supported on functionalized carbon nanotubes and their performance in the oxidation of thiophenol with O 2. We show that single gold atoms are not active, but they aggregate under reaction conditions into gold clusters of low atomicity that exhibit a catalytic activity comparable to that of sulfhydryl oxidase enzymes. When clusters grow into larger nanoparticles, catalyst activity drops to zero. Theoretical calculations show that gold clusters are able to activate thiophenol and O 2 simultaneously, and larger nanoparticles are passivated by strongly adsorbed thiolates. The combination of both reactants activation and facile product desorption makes gold clusters excellent catalysts.
Bibliographical noteFunding Information:
Financial support from the Spanish Science and Innovation Ministry (Consolider Ingenio 2010-MULTICAT CSD2009-00050, Subprograma de apoyo a Centros y Universidades de Excelencia Severo Ochoa SEV 2012 0267, MAT2011-28009 and MAT2010-20442 projects) and Xunta de Galicia (Grupos Ref.Comp.2010/41) is acknowledged. M.J.Y. and E.L. acknowledge the support of the National Centre for Research Resources (5 G12RR013646-12) and the National Institute on Minority Health and Health Disparities (G12MD007591) from the National Institutes of Health and of the National Science Foundation for support with grants DMR-1103730 and PREM: NSF PREM Grant # DMR 0934218. We also acknowledge the support of Consejo Nacional De Ciencia y Tecnología. J.N. expresses his gratitude to Consejo Superior de Investigaciones Científicas for a JAE Fellowship.