Surface-enhanced infrared absorption of CO on platinized platinum

We report here the first observation of surface-enhanced infrared spectrosc opy on platinized platinum surfaces, as well as a thorough explanation of t he resulting spectra, Smooth platinum electrodes were electrochemically pla tinized to produce regular metal island surfaces that led to enhanced absor ption of the infrared spectrum of adsorbed carbon monoxide, The infrared sp ectrum of CO adsorbed from an aqueous electrolyte onto the electrode surfac e was measured in situ by external reflection spectrometry. The amount of a dsorbed CO was estimated from the difference spectrum before and after the CO was oxidized to CO2 by finding the ratio of the absorbance of adsorbed C O prior to oxidation to the absorbance of dissolved carbon dioxide formed w hen the adsorbed CO was oxidized. By varying the platinization conditions, platinized Pt surfaces that yielded IR band enhancements of up to 20 times that of CO adsorbed on smooth Pt electrodes were prepared. When CO was adso rbed on a smooth Pt electrode, the shape of the band due to the CO stretchi ng mode was quite symmetrical. As the degree of platinization was increased , the band became asymmetrical, then bipolar, and finally appeared as a ref lection maximum. This behavior was simulated using the Bergman representati on of effective dielectric function.