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Study of the Formic Acid Electrooxidation on Rhodium on Steady State Using a Flow Cell: Potential Dependence of the CO Coverage

Authors
  • Luque, Gisela C.1
  • Montero, María A.1
  • Gennero de Chialvo, María R.1
  • Chialvo, Abel C.1
  • 1 Instituto de Química Aplicada del Litoral, IQAL (UNL-CONICET), Programa de Electroquímica Aplicada e Ingeniería Electroquímica, PRELINE (FIQ-UNL), Santiago del Estero, Santa Fe, 2829, Argentina , Santiago del Estero (Argentina)
Type
Published Article
Journal
Electrocatalysis
Publisher
Springer US
Publication Date
Apr 12, 2020
Volume
11
Issue
4
Pages
405–412
Identifiers
DOI: 10.1007/s12678-020-00599-7
Source
Springer Nature
Keywords
License
Yellow

Abstract

The HCOOH electrooxidation reaction (FAO) was experimentally studied on rhodium electrode using a flow cell in a 0.5-M HCOOH + 0.5-M H2SO4 solution. It was obtained the steady-state current-potential curve by chronoamperometry, which demonstrated that the FAO is verified in the potential region 0.45 < E/V < 0.70. The amount of adsorbed CO on the electrode surface as a function of potential was quantified by stripping voltammetry after changing to a 0.50-M H2SO4 solution at closed electric circuit. It was established that the spontaneous dissociative adsorption of HCOOH on rhodium produces irreversibly adsorbed CO only for potential values E ≤ 0.40 V, and therefore, the FAO takes place in the absence of COad. These results can explain the current-potential profiles obtained when the FAO is studied by cyclic voltammetry at different values of the potential scan limits, where the behaviour is strongly influenced by the inhibition of reaction sites due to the adsorbed CO. A kinetic mechanism for the FAO on rhodium is proposed on the basis of the results obtained, which are also in agreement with recently published spectroscopic measurements. Graphical AbstractThe kinetics of the formic acid electrooxidation reaction (FAO) on rhodium electrode on steady state was studied. It was demonstrated that adsorbed CO is not a reaction intermediate, being only an inhibitor. A kinetic mechanism compatible with experimental as well as previous spectroscopic evidences was proposed.

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