Silica-Supported Au and Pt Nanoparticles and CO Adsorption
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Silica-Supported Au and Pt Nanoparticles and CO Adsorption Derrick Mott, Jin Luo, Andrew Smith, Wai-Pan Chan, William Bozza, Anjana Sarkhel, Sara Park, and Chuan-Jian Zhong* Department of Chemistry, State University of New York at Binghamton, Binghamton, New York 13902, USA. * [email protected]
ABSTRACT The understanding of the surface properties of metal nanoparticles is essential for exploiting their unique catalytic properties. This paper reports findings of the preparation of silica-supported Pt and Au nanoparticles and the FTIR characterization of CO adsorption on the supported nanoparticles. The nanoparticles were prepared by both a traditional impregnation method and molecular-capping based synthesis method. By comparing the spectroscopic characteristics of CO adsorption on these catalysts, similarities and differences in CO stretching bands have been identified. The findings are significant because important insights have been gained into the surface binding properties of Au and Pt nanoparticle catalysts.
INTRODUCTION The detailed structure of surface sites of metal catalysts is important in the catalytic oxidation of carbon monoxide (CO). Examples of CO oxidation can be found in water-gas shift reaction, emission control in catalytic converters, and fuel cell reactions such as methanol reforming and methanol oxidation in fuel cells. The development of fuel cell catalysts with high activity, selectivity and low cost is a challenging task. While platinum catalysts have been extensively studied, the poisoning of the catalysts by adsorbed CO species is a major problem [1-7]. Recently, gold-based nanoparticles supported on oxides have been shown to exhibit unprecedented low temperature catalytic activity for CO oxidation [8-12] and other reactions [13]. The understanding of the surface properties of gold nanoparticles is essential for exploiting the unique catalytic properties. This paper reports results of the characterization of silica-supported monometallic gold and platinum catalysts prepared by the insipient wetness impregnation method [14] and molecular-capping based synthesis method [15]. CO is a powerful spectroscopic probe, and FTIR study of this probe allow us to address some of the fundamental issues in understanding the surface properties and reactivities of metallic catalysts [16]. Because CO adsorption is highly sensitive to the surface sites, the analysis of the diagnostic CO stretching bands [17] provides information for assessing the surface binding properties. While there are many infrared spectroscopic studies of CO adsorption on gold and platinum catalysts [8,11,14,17], there are relatively limited studies on how differences in catalyst preparation could lead to differences in the observed CO stretching bands.
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EXPERIMENTAL Gold nanoparticles of 2-nm core size encapsulated with an organic shell were synthesized by the two-phase method [18]. Platinum nanoparticles of 2-nm core size encapsulated with an organic shell were synthesized using a thermal reducti
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