Modeling of Solid Oxide Fuel Cells with Linear and Nonlinear Functionally Graded Electrodes

Abstract

Solid Oxide Fuel Cells (SOFCs) have demonstrated high efficiency in full scale trials and are a possible partial solution to maximizing dwindling fossil fuel resources. Functionally graded electrodes have previously been investigated to improve SOFCs performance with optimized microstructure. However, little investigative focus has been put on optimal power output for given electrode microstructures. In this work, a multiscale and multiphysics full cell electrode polarization model of SOFCs has been expanded and developed to incorporate both electrodes microstructure. The macromodel describes the overall cell behavior through activation, Ohmic, and concentration losses based on chemical and concentration potentials. The micromodel outputs effective resistivity of the porous electrode based on microstructural parameters such as pore diameter, particle size, and reaction area. The integration of macro- and micromodels is achieved by passing the micromodel parameters to the macromodel during the solution procedure. The cell-level SOFC model has been utilized to reveal the complex relationship between the transport phenomena, which includes the transports of electron, ion and gas molecules through the electrode and the electrochemical reaction at the triple phase boundaries. The work contributes to our understanding of the cell performance in relation to graded microstructures. The performance of functionally graded electrodes has been analyzed to understand the implications of varying the electrode microstructure. The design guidelines provides in the study can aid selection and development of fabrication process that can further improve SOFC performance.