Model for Solid Electrolyte Gas Electrode Reaction Kinetics; Key Concepts, Basic Model Construction, Extension of Models, New Experimental Techniques for Model Confirmation, and Future Prospects

Abstract

In order to survey history and state of art of theoretical and kinetic studies of gas electrode reaction on solid oxide electrolyte, overview was made on the research works reported by the author and his co-investigators. Through reviewing their works, frontier of research is clarified. It was shown that electrode reaction is controlled by nonfaradaic chemical reaction process, and the nature of the overpotential is the chemical potential deviation of the interface from equilibrium state. Mechanical stress at the electrode/solid electrolyte interface is considered varying with the overpotential. Importance is emphasized for mechano-electrochemistry, the field to study the relationship of electrochemistry and mechanical property of the electrochemical cells.

Pinning-down polarization losses and electrode kinetics in cermet-supported LSM solid oxide cells in reversible operation

“…The observation in the present work appears different from the behavior of Pt electrodes [46,[20][21][22]. There, the inverse of the resistance, σ E , exhibits a characteristic dependence of pO 2 +1/2 and pO 2 −1/2 with a broad maximum.…”

“…According to non-faradaic mechanism as suggested by Mizusaki et al [20,21,4,22], similarly as the metallic Pt and Ni electrodes, surface diffusion and surface adsorption/desorption reaction are considered for the rate controlling steps for predominantly electronic conductor LSM electrode materials [20,21,41,42,14,22]. When the transport paths and reaction sites on LSM surface near triple phase boundaries charge transfer is involved but in a very facile way so that the electrode reaction is Fig.…”

“…From the parametric analysis of porous gas electrodes of Ni-YSZ and LSM-YSZ the surface diffusivity, D = (r S c P ) −1 , and surface adsorption reaction constant k = (r P c P ) −1 as rate-controlling processes which is in the framework of the electrode reaction theory since long suggested by Mizusaki et al [20,21]. As emphasized in his recent review on this issue [22], the Butler-Volmer type activation polarization in the liquid electrochemistry originates from the solvation, which does not apply to charge carriers in solid phase. The charge transfer reaction at solid-solid interface is thus generally facile in the flat-band condition.…”

“…Therefore the charge transfer process generally is not considered rate-controlling in solid electrolyte gas electrode reaction. Apparent Butler-Volmer type relationship, if any, can be also explained by the non-faradaic chemical reaction controlled kinetics, since the chemical potential is directly related to the electrical potential of the cell by the Nernst equation [20][21][22].…”

Application of a General Gas Electrode Model to Ni-YSZ Symmetric Cells: Humidity and Current Collector Effects

“…This point has been emphasized by Prof. Mizusaki and coworkers over the decades. 4,[23][24][25][26][27] Recently, a review has been published 28) in which these issues are, probably for first time, directly and explicitly addressed.…”