Modeling impedance diagrams of active layers in gas diffusion electrodes: diffusion, ohmic drop effects and multistep reactions

Yann Bultel (1) , Laurence Géniès (1) , O. Antoine (2) , Patrick Ozil (1) , Robert Durand (1)

1 LEPMI - Laboratoire d'Electrochimie et de Physico-chimie des Matériaux et des Interfaces
2 Laboratory of Photonics and Interfaces

The dc and ac responses of an active layer in a gas diffusion electrode (GDE) have been predicted from theory, considering both diffusion and ionic ohmic drop inside the active layer and a multistep mechanism. This complete approach required numerical resolution. One-step, two-step (Volmer–Heyrovsky) and three-step mechanisms have been investigated. Numerical simulations from original models using dimensionless parameters lead to impedance diagrams involving a nearly perfect semicircle at low frequency and a 45° angle straight line at high frequency, so proving, respectively, the influence of mass and charge transport processes. Finally, a three-step oxygen reduction mechanism gives rise to theoretical impedance diagrams similar to the experimental ones.

Mots clés: Active layer; Gas diffusion electrode; Multistep reaction; Modeling; Ac impedance

Domaines: Matériaux

Yann Bultel, Laurence Géniès, O. Antoine, Patrick Ozil, Robert Durand. Modeling impedance diagrams of active layers in gas diffusion electrodes: diffusion, ohmic drop effects and multistep reactions. Journal of electroanalytical chemistry and interfacial electrochemistry, 2002, 527 (1-2), pp. 143-155. ⟨10.1016/S0022-0728(02)00835-5⟩. ⟨hal-00418106⟩