Reaction kinetics of the Pt, O2(g)|c-ZrO2 system: precursor-mediated adsorption

• Published in: Solid state ionics Vol. 120; no. 1-4; pp. 211 - 225
• Main Authors: Mitterdorfer, A., Gauckler, L.J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-05-1999; Elsevier Science
• Subjects: Chemistry; Digital simulation; Electrochemical kinetics; Electrochemistry; Exact sciences and technology; General and physical chemistry; Impedance spectroscopy; Kinetics and mechanism of reactions; Solid oxide fuel cell; State space model; State space model; Impedance spectroscopy; Solid oxide fuel cell; Digital simulation; Electrochemical kinetics; Oxygen; Electrical conductivity; Porous electrode; Solid electrolyte; Theoretical study; Electrode electrolyte interface; Transition metal; Stabilized zirconia; State space method; Inorganic compound; Kinetic model; Partial pressure; Yttrium Oxides; Adsorption; Platinum; Reaction mechanism; Numerical simulation; Electrochemical reaction; Electrical impedance
• ISSN: 0167-2738; 1872-7689
• DOI: 10.1016/S0167-2738(98)00472-X

A micro kinetic model of the Pt, O2(g)|c-zirconia electrode/electrolyte system was developed in state space form (model M3). The oxygen adsorption/desorption process was modeled as a precursor-mediated surface reaction. The surface diffusion of atomic oxygen and the electrochemical reduction of atomic oxygen near the three-phase boundary (tpb) were considered. It was shown that the simulated charge-transfer behavior of M3 is significantly different from models with ordinary Langmuir kinetics (model M2). The electrochemical rate constant was estimated from selected experimental data as k10=(6.05±0.25)·106 m3/(mol·s). From experimental results it was concluded that only one adsorbed oxygen species is relevant for the dynamic behavior. In porous Pt electrodes binary gas phase diffusion of oxygen in O2/N2 gas mixtures becomes relevant at oxygen partial pressures below ∼10−3 atm. The general procedure for state and parameter estimation can be well adopted for the investigation of further reaction mechanisms.