Dynamic first-principles molecular-scale model for solid oxide fuel cells

Abstract

This model for voltage V vs. current density i characteristics applies both to the Solid Oxide Fuel Cell (SOFC) and Solid Oxide Electrolysis Cell (SOEC) modes of operation. It is based on reaction rates calculated from a molecular-scale model for the physical and chemical processes involved. An expression is obtained for i as a function of activation polarization Vact at either interface. For large applied positive or negative voltage it correctly predicts i to be based respectively on the reverse reaction or forward reaction attempt rate. In contrast, the Butler-Volmer i(Vact) expression incorrectly predicts infinite i for infinite applied voltage. The model expression for V(i) takes open- circuit emf, activation polarization, concentration polarization, and ohmic polarization into account. Its predictions agree quite well with experiment results obtained by another group.