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Agradecimentos: The authors would like to acknowledge IIT Kanpur for providing all the facilities to carry out the experiments of the present study. YMJ thanks Sao Paulo Research Foundation (FAPESP) Grant No. 2016/12341-5 for financial support. YMJ and DSG thank the Center for Computational Engineering and Sciences at Unicamp for financial support through the FAPESP/CEPID Grant # 2013/08293-7. The authors (MMD and KB) would like to thank Advanced Imaging Centre for electron microscopic characterization Abstract: Selective oxidation of CO to CO2 using metallic or alloy nanoparticles as catalysts can solve two major problems of energy requirements and environmental pollution. Achieving 100% conversion efficiency at a lower temperature is a very important goal. This requires sustained efforts to design and develop novel supported catalysts containing alloy nanoparticles. In this regard, the decoration of nanoalloys with graphene, as a support for the catalyst, can provide a novel structure due to the synergic effect of the nanoalloys and graphene. Here, we demonstrate the effect of nano-PdPt (Palladium-Platinum) alloys having different morphologies on the catalytic efficiency for the selective oxidation of CO. Efforts were made to prepare different morphologies of PdPt alloy nanoparticles with the advantage of tuning the capping agent (PVP - polyvinyl pyrollidone) and decorating them on graphene sheets via the wet-chemical route. The catalytic activity of the G-PdPt hybrids with an urchin-like morphology has been found to be superior (higher % conversion at 135 degrees C lower) to that with a nanoflower morphology. The above experimental observations are further supported by molecular dynamics (MD) simulations FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP Fechado

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

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:49:05Z No. of bitstreams: 0 Made available in DSpace on 2013-08-22T18:49:05Z (GMT). No. of bitstreams: 0 Previous issue date: 1997-01-01 Made available in DSpace on 2013-09-30T19:09:18Z (GMT). No. of bitstreams: 0 Previous issue date: 1997-01-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T14:19:38Z No. of bitstreams: 0 Made available in DSpace on 2014-05-20T14:19:38Z (GMT). No. of bitstreams: 0 Previous issue date: 1997-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação para o Desenvolvimento da UNESP (FUNDUNESP) Estudou-se e discutiu-se os diferentes métodos de preparação de microfios de Pt pura, Pt-Ir (20%, m/m) e Pt-Rh (10%, m/m) a serem empregados na construção dos respectivos microeletrodos. Os fios de Pt e suas ligas foram obtidos empregando fieiras com diferentes diâmetros. em seguida foi utilizado o procedimento de desgaste eletroquímico em sal fundido (mistura NaNO3/ NaCl 14: a 320oC) para a Pt e em solução 6 molL-1 NaCN + 2 mol L-1 NaOH para a liga de Pt-Ir. Para a caracterização da interface metal-vidro e determinação dos raios geométrico e efetivo foram empregadas as microscopias óptica e eletrônica de varredura, a voltametria cíclica e a cronoamperometria. A condição de selagem foi verificada através dos gráficos da capacitância aparente Cd, corrigida considerando-se a área dos microeletrodos, e a velocidade de varredura, v. Platinum, platinum-iridium (20 wt.%) and platinum-rhodium (10 wt.%) alloys were prepared as microwires using different methods. Microwires of Pt and its alloys with several diameters were prepared by passing wires of 1 mm of diameter through a drawplate. Afterwards, the Pt microwire was weared electrochemically in a fused salt mixture (NaNO3/NaCl: 4:1; 320°C) applying a square potential wave (1-50 Hz; 2.5 V). Microwires of Pt-Ir and Pt-Rh alloys were prepared applying a sine-shaped AC potential wave (60 Hz, 3-8 V rms), in 6 M NaCN + 2 M NaOH aqueous solution. The characterization of the interface metal-insulating material and the determination of geometric and effective radii of microelectrodes were carried out by means of optical and scanning electron microscopy, cyclic voltammetry and cronoamperometry. The Cd - v plot, where Cd is the apparent capacitance corrected by the electrode area and v the scan potential sweep was used to verify the interface metal-glass sealing conditions. Universidade Estadual de São Paulo Instituto de Química Departamento de Química Analítica Universidade Estadual de São Paulo Instituto de Química Departamento de Físico-Química