ReaxFF reactive force field for solid oxide fuel cell systems with application to oxygen ion transport in yttria-stabilized zirconia

We present the ReaxFF reactive force field developed to provide a first-principles-based description of oxygen ion transport through yttria-stabilized zirconia (YSZ) solid oxide fuel cell (SOFC) membranes. All parameters for ReaxFF were optimized to reproduce quantum mechanical (QM) calculations on relevant condensed phase and cluster systems. We validated the use of ReaxFF for fuel cell applications by using it in molecular dynamics (MD) simulations to predict the oxygen ion diffusion coefficient in yttria-stabilized zirconia as a function of temperature. These values are in excellent agreement with experimental results, setting the stage for the use of ReaxFF to model the transport of oxygen ions through the YSZ electrolyte for SOFC. Because ReaxFF descriptions are already available for some catalysts (e.g., Ni and Pt) and under development for other high-temperature catalysts, we can now consider fully first-principles-based simulations of the critical functions in SOFC, enabling the possibility of in silico optimization of these materials. That is, we can now consider using theory and simulation to examine the effect of materials modifications on both the catalysts and transport processes in SOFC.