A kinetic study on oxygen redox reaction of a double-perovskite reversible oxygen electrode— Part II: Modelling analysis

Abstract

Mixed ionic and electronic conductor double perovskites are very promising oxygen electrode materials for solid oxide cell technology. However, understanding their specific kinetic mechanism is a fundamental preliminary step towards detecting the best reachable performance, optimising the operation conditions and the electrode architecture. Indeed, the contributions of different rate-determining steps can vary as a function of the working point. In this framework, after a detailed experimental campaign devoted to the study of SmBa_0.8Ca_0.2Co₂O_5+δ (SBCCO) oxygen electrode behaviour, the authors propose a theoretical analysis of oxygen reduction and oxygen evolution reaction paths that couples a preliminary study through equivalent circuit analysis with a physics-based model to predict the operation of SBCCO as a reversible oxygen electrode. Following a semi-empirical approach, the kinetics formulation was derived from thermodynamics and electrochemistry fundamental principles and was tuned on electrochemical impedance spectroscopy (EIS) spectra in order to retrieve the unknown kinetic parameters. The successful cross-checking of the simulated results with the experimental data obtained by direct current measurements validated the proposed model, here applicable in further works on full cells to simulate the SBCCO oxygen reversible electrode performance.