Promotion effect of platinum on gold’s reactivity : a high-resolution photoelectron spectroscopy study

Agradecimentos: We thank Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP-07/54829-5) and Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) for financial support. Special thanks to Prof. G. Tremiliosi-Filho for lending the Au(332) crystal. M.J.P. and E.A.C. thank FAPESP and CNPq for the fellowships granted (Proc. FAPESP 2011/12.566-3; Proc. CNPq 150192/2014-2). We also thank the Brazilian Synchrotron Light Source for the beam time and the PGM-beamline staff for support during the experiments Abstract: The reactivity of the Pt/Au(332) surface was studied using high-resolution photoelectron spectroscopy and carbon monoxide adsorption at 3.5 x 10(-3) mbar. The characterization of Pt/Au(332) indicates the formation of a Au-Pt surface alloy at the topmost atomic layer of the (332) crystal due to an atomic exchange mechanism at both terrace and step edge. The amount of alloyed Au atoms has proven to be dependent on the amount of Pt deposited in the coverage range investigated. The activation of Au atoms by alloying is detected by comparing the ability of the surface to adsorb CO at high pressures. By analyzing the C 1s and O 1s photoemission lines it is possible to conclude that CO adsorption is both dissociative and molecular on the PtAu/Au(332) surface, differently from the behavior observed for Au and Pt single crystals. Also, by rising the temperature of the COads-PtAu/Au(332) surface, a dissociative reaction path is followed by the accumulation of graphitic carbon on the surface and the oxygen/carbon dioxide desorption. Thus, our results show not only the differential catalytic behavior of Pt@Au/Au(hkl) model surfaces but also that Au atoms have an active role on the reaction mechanism FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ Aberto