Infrared band spectroscopy supported metals

The adsorption of CO followed by infrared (IR) spectroscopy has long been used to characterise supported and unsupported transition metals [106]. CO adsorbed on atop sites gives IR bands in the range 2100-2040 cm while bridging and three-fold CO give bands in the range 1860-1780 cm . Extensive studies on monometallic systems have led researchers to assign individual peaks in a bimetallic system to CO adsorbed to each individual component. The... 

The feasibility of determining approximately the surface composition of silica-supported Ru-Pt catalysts by using infrared spectroscopy and two adsorbing gases has been explored, as a possible alternative to more complex instrumental methods and with the advantage of greater sensitivity to the outermost surface layer. The infrared absorption bands of CO selectively adsorbed on Pt sites and NO selectively adsorbed on Ru sites were stable in vacuo at room temperature. If both extinction coefficients and stoicheiometric coefficients are taken to be independent of surface composition, a simple correlation between the absorbance ratio and the bulk metal composition was obtained, suggesting that the surface and bulk compositions were similar. 

In early in-situ infrared spectroscopy studies of catalyst supported on reflective Au substrates, it was recognized that spectral bands develop distortions due to anomalous optical effects as the catalyst coverage becomes greater than a few monolayers [17, 18, 158]. Different procedures were adopted to ensure that catalyst coverages on Au remained low [15, 17, 18, 157, 158]. Related to these efforts are experiments that examine the electrochemical and optical properties of nanostructured metal electrodes prepared by chemical, vapor, or electrochemical deposition methods (cf. Refs. [79, 137, 141, 170-179] and references therein). Much of the work in this area has targeted SEIRAS measurements. 

The analysis of thin films is often performed by infrared spectroscopy. Compared to reflection absorption measurements on metal surfaces using p-polarized fight at grazing incidence, investigation of self-supported thin films or of thin films on transparent substrates shows weaker infrared absorption bands. Weaker absorption bands are caused by the absence of the surface enhancement mechanism and the poorer reflectivity. On the other hand, due to the absence of the metal selection rule, spectra of p- and s-polarization can be recorded in the case of freestanding films or of transparent substrates. Complex spectral features may arise... 

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