Proton-polaron and thermionic identity of BaCeO3 polymorph for intermediate temperature fuel cell technology: A first principles and molecular dynamics approach

Abstract

This study employs first principles and classical molecular dynamics approach to investigate distinct proton landscape and scattering events among aristotype and hettotype BaCeO3 polymorph. We systematically sampled different migration pathways to examine the thermionic behaviour and lattice disorder against the activation energy profile as a function of operating temperatures. According to DFT outcomes, the asymmetric landscape among hettotype structures entails a feeble vacancy formation energy (Evac = 0.326 eV and 0.485 eV) with noticeable lattice strain (ε = 0.258 % and 0.167 %) and desirable proton transfer pathway relative to aristotype counterpart. The transport characteristics from molecular dynamics on the other hand reveals an accelerated proton transfer at intermediate temperatures (300–550 °C) due to symmetric hydrogen bonding around the proton neighbourhood with a curtailed translational barrier from the low frequency lattice phonons. However, repellent response at elevated temperatures (>550 °C) illustrates the advent of ambipolar characteristics (H+/O2−), structural phase transitions, defect scattering events and the rise of artificial barrier as localized proton traps via proton polaron and defect (VO..) interactions. The study as a result accentuates the demand of structural and dynamical coherence to extend the commercial utility of BaCeO3 polymorph for the fuel cell technology.