Site effects in the adsorption of carbon monoxide on real 1.8 nm Pt nanoparticles: An Infrared investigation in time and temperature

• In situ DRIFT targets CO adsorption on the standard Pt reference catalyst EuroPt-1.
• The 55-atom Pt cuboctahedra exhibit three different sites: faces, edges and corners.
• The method to analyze the complex spectrum of CO adsorbed on Pt is detailed.
• IR frequencies come: face, edge, corner, and multiple adsorptions on a single corner.
• Three parameters are studied: CO partial pressure, temperature and time.

A study using in situ Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy has targeted carbon monoxide (CO) adsorption on the standard platinum (Pt) reference catalyst EuroPt-1. Reduced and non-reduced EuroPt-1 were analyzed in an infrared (IR) chamber which allowed the control of the CO atmosphere from temperatures ranging from −30 to 300 °C. The complex spectra of CO linearly adsorbed on highly dispersed Pt have been analyzed by using a combination of Fourier self-deconvolution and curve fitting. The linear-CO spectrum is composed of three main bands at 2096, 2083 and 2072 cm−1. These were attributed to the three different adsorption sites – faces, edges and corners – of the 55-atom cuboctahedron Pt particles. The adsorption site competition was followed as a function of the temperature and it was demonstrated that these sites were never completely covered with CO. Furthermore, non-reduced EuroPt-1 presented reversible oxygen binding at low temperature in competition with CO. At 300 °C, CO mainly occupied corner sites and a comparable state was approached for both catalysts by the removal of the oxygen from these corner sites.

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