Microkinetic Modeling of CO2 and H2O Electrolysis on Ni in a Solid Oxide Electrolysis Cell: A Critical Evaluation

Solid oxide cells (SOC) are ideal candidates for the electrochemical conversion of H2O and CO2 into H-2 and CO using renewable sources. This work develops different electrochemical models for the reduction of H2O and CO2 based on elementary step kinetics and discriminates them based on their ability to predict experimentally measured cell performances. The thermo-catalytic chemistry is represented using a micro kinetic model, which is coupled to the electrochemical model through the surface coverage terms. A one dimensional representation of SOC resolving the cell across the thickness of the electrodes is used for simulations. The source terms for the species transport Eqs. are calculated using the micro kinetic model by applying mean field approximation. The discussion in the paper covers aspects related to parameter fitting, model development, solution methodology, model discrimination and identification of rate limiting step.