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Thermodynamic Studies of Anion Adsorption at Stepped Platinum( h kl ) Electrode Surfaces in Sulfuric Acid Solutions

2002; American Chemical Society; Volume: 106; Issue: 49 Linguagem: Inglês

10.1021/jp026561p

1520-6106

Jorge Mostany, Enrique Herrero, Juan M. Feliú, Jacek Lipkowski,

Electrocatalysts for Energy Conversion

The thermodynamics of the so-called perfectly polarized electrode was employed to analyze the total charge densities for stepped Pt(hkl) electrodes in solutions of H2SO4 with an excess of an inert electrolyte (0.1 M HClO4). Three Pt single-crystal electrodesPt(10,10,9) = 20(111)×(111), Pt(7,7,6) = 14(111)×(111), and Pt(5,5,4) = 10(111)×(111)vicinal to the Pt(111) surface were employed in these studies. A complete thermodynamic analysis using the electrode potential and the charge as independent variables has been performed. The Gibbs excess, Gibbs energy of adsorption, electrosorption valency, and Esin−Markov coefficients for (bi)sulfate adsorption at these surfaces have been determined. The thermodynamic data display a dependence on the crystallographic structure of the Pt electrode surface. Both the Gibbs excess and the Gibbs energy of adsorption decrease with increasing step density or decreasing terrace length. This result indicates that adsorption of (bi)sulfate is stronger at larger (111) terraces.