Prediction of overpotential and concentration profiles in solid oxide fuel cell based on improved analytical model of charge and mass transfer

摘要

The accuracy of prediction of overpotential and relevant concentration distributions is important for understanding fundamentals and electrochemical reaction engineering. The conventional linear approximation (CLA) of the exponent items in the Butler-Volmer kinetics causes significant discrepancies in the estimation of the overpotential profile at moderate and high electric loads. Based on a one-dimension dimensionless charge transfer model, an approach of linear translation (LT) is presented to solve the problem of the CLA and improve the power-law (PL) approach of nonlinear approximation (J Power Sources, 210 (2012) 67-80), which is accurate at high current densities but is still limited to cases of thick electrodes. The hybrid LT + PL approach is then convincingly validated in a wide range of fuel cell operations, including moderate and high operating current densities, electrolyte- and electrode-supported electrodes, and asymmetric anodic and cathodic transfer , coefficients. Then the analytical species concentration profiles are obtained from a decoupled charge/mass transfer model. The closed-form electrode-level model significantly improves the computational efficiency in thermo-electrochemical cell-level simulation. Although discussed in the context of solid oxide fuel cells, the approaches in this work are applicable to general electrochemical systems which hold Butler-Volmer kinetics.