CARBON MONOXIDE ADSORPTION ON Pt MONOLAYER ON Pd(hkl) SURFACE STUDIED BY SUBTRACTIVELY NORMALIZED INTERFACIAL FOURIER TRANSFORM INFRA-RED SPECTROSCOPY

The progress of our civilization is critically dependent on the discovery of new materials and structures with better properties, novel functionality and applications. The ultra thin metal overlayers represent one class of such structures with increasing application in fuel cells. In our work, the two-dimensional Pt monolayers on Pd(hkl) were used as model system to study CO adsorption. The PtML/Pd(hkl) were obtained using surface limited red-ox replacement reaction of underpotentially deposited Cu monolayers on Pd(hkl) with, and without presence of citrate in the reaction solution. The strength of the CO adsorption on Pt monolayer was studied by subtractevily normalized interfacial fourier transform infra-red spectroscopy (SNIFTIRS). The SNIFTIRS results indicate synergistic effect of both; Pt monolayer and Pd(hkl), yielding a qualitatively new phenomenon where the bond of adsorbed CO on PtML/Pd(hkl) is weaker than the corresponding CO bond on each of the bulk metal surfaces. This result has fundamental importance when catalysts for oxygen reduction and hydrogen oxidation reactions are considered where the surface poisoning by intermediates or impurities is responsible for reduced catalyst activity.