Comparative electrochemical behaviour of CO₂ on Pt and Rh electrodes in acid solution

• Autores: Marcos, M. L.; González-Velasco, J.; Bolzán, Agustín Eduardo; Arvia, Alejandro Jorge
• Año de publicación: 1995
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Ciencias Exactas; Química; CO2 electrochemistry; Acid solutions
• Institución: Universidad Nacional de La Plata

The electroformation of adsorbed species on Pt and Rh from CO₂ dissolved in aqueous 0.5 M H₂SO₄ and the influence of adsorbed species on the hydrogen evolution reaction (HER) were examined for smooth and columnar structured Pt and smooth and rhodized Rh electrodes at 25|dgC. Different electrosorbed species resulting from the adsorption of CO₂ on Rh were found. The electro-oxidation of these adsorbates on Rh takes place over a potential range larger than that for adsorbates on Pt, overlapping the potential range of electroformation of the O-containing layer. A part of the reduced CO₂ adsorbates on Rh behaves as CO-like adsorbates. The presence of adsorbed species from CO₂ influences differently the stationary HER current potential curves for both types of Pt and Rh electrodes. In the range of low current density (cd), the Tafel slope for Pt is −0.030 V decade⁻¹. Conversely, the presence of a chemisorbed species on Rh changes the Tafel slope for the HER in the range of low cd from −0.030 V decade⁻¹ for CO₂-free solutions to −0.120 V decade⁻¹ for CO₂-saturated solution. These changes are explained by a modification in the rate-determining step of the HER produced by chemisorbed species.
Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas