The Kinetics Effect in SOFCs on Heat and Mass Transfer Limitations: Interparticle, Interphase and Intraparticle Transport

The transport processes in the porous, micro-structured electrodes are one of the least understood areas of research of the solid oxide fuel cell (SOFC). To enhance the knowledge of the transport process’ impact on the performance in the electrodes, the micro-structure needs to be modeled in detail. But at these smaller scales, it can be both cost and time saving to first conclude at which scales, the limiting action on the transport processes occurs. This study investigates the limiting effect of the kinetic parameters’ on the heat and mass transfer at interparticle, interphase and intraparticle transport level. The internal reaction and the electrochemical reaction rates are studied at three levels in the microscopic range or even smaller. At the intraparticle level the effect of temperature distribution, i.e., heat transfer, within a catalyst particle is often less limiting than the internal mass diffusion process, while at the interphase level the former is more limiting. In this study, no severe risk for transport limitations for the anode and the cathode of the SOFC was found with the chosen kinetic parameters. It was found that the reaction rates constitute the largest risk. A parameter study was conducted by increasing the steam reforming and the electrochemical reaction rates by a factor of 100 without any transport limitations for the same kinetic parameters. The result of this study provides one type of control of the kinetic parameters which in turn have an impact on the reforming reaction rates and the cell performance.