The Effect Of Specific Chloride Adsorption On The Electrochemicalbehavior Of Ultrathin Pd Films Deposited On Pt111 In Acidsolution

Download or read book The Effect of Specific Chloride Adsorption on the Electrochemicalbehavior of Ultrathin Pd Films Deposited on Pt(111) in Acidsolution written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The electrochemical behavior of thin Pd films supported on a Pt(111) electrode is investigated by cyclic voltammetry (CV) and in-situ Fourier transform infrared (FTIR) spectroscopy. It is demonstrated that in perchloric acid solution underpotential deposition of hydrogen (H{sub upd}) and hydroxyl adsorption (OH{sub ad}) is in strong competition with the adsorption of Cl- anions, the latter being present as a trace impurity in HClO4. The interaction of Cl- with Pd is rather strong, controlling the adsorption of H{sub upd} and OH{sub ad} as well as the kinetic rate of CO oxidation. The microscopic insight (the binding sites) of the adsorbed CO (CO{sub ad}) and the rate of CO oxidation (established from CO2 production) on Pt(111) modified with a (sub)monolayer of Pd is elucidated by means of Fourier infrared (FTIR) spectroscopy. The appearance of both the characteristic Pt(111)-CO{sub ad} and Pt(111)1 ML Pd-CO{sub ad} stretching bands on a Pt(111) surface covered by 0.5 ML Pd confirms previous findings that the Pd atoms agglomerate into islands and that the bare Pt areas and the Pd islands behave according to their own surface chemistry. The systematic increase of the Pd surface coverage results in a gradual change in the catalytic properties of Pt(111)-xPd electrodes towards CO oxidation, from those characteristic of bare Pt(111) to those which are characteristic for Pt(111) covered with 1 ML of Pd.