High-entropy cathodes with Cr and CO2 tolerance via the combination of Ba0.5Sr0.5Co0.8Fe0.2O3-δ and Nd, Ni, Zr ternary doping for both oxygen ion and proton conducting solid oxide fuel cells

Abstract

The sluggish kinetics of oxygen reduction reaction (ORR) and the degradation of cathodes caused by Cr and CO₂ poisoning are major obstacles to the commercial application of solid oxide fuel cells (SOFCs). It is still challenging to achieve composite cathodes with both high ORR activity and excellent Cr, CO₂ tolerance, and design composite cathodes suitable for both oxygen ion and proton SOFCs. Taking advantage of high-entropy materials, here, we report our findings in harnessing high-throughput computational methods to expedite the design of novel composite cathodes based on Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) as the matrix. We methodically compute the lattice substitution energy (E_ls), O projected density of states (O p-Dos), and the work function for a set of 13-element candidates. Our research underscores BNSCNZF (Ba_0.4Nd_0.1Sr_0.5Co_0.6Ni_0.1Zr_0.1Fe_0.2O_3-δ), the combination of BSCF and Nd, Ni, Zr ternary doping, as a promising and revolutionary candidate, exhibiting superior performance in terms of electronic conductivity, oxygen adsorption, and transport activity compared to the established BSCF series. BNSCNZF incorporating Sm_0.2Ce_0.8O_2-δ (SDC) and BaZr_0.1Ce_0.7Y_0.2O_3-δ (BZCY) as the electrolyte achieves very low polarization resistances (R_p) in the symmetric cell mode (0.02 Ω cm⁻² and 0.56 Ω cm⁻² at 700 °C, respectively). BNSCNZF also exhibits excellent tolerance to Cr and CO₂ poisoning due to its higher energy barriers for impurity generation and higher absorption energy of produced impurities from the matrix. The oxide ion and proton single cells with BNSCNZF exhibit excellent power densities of 1.21 W cm⁻² and 0.63 W cm⁻² at 700 °C, respectively, which are higher than that with BSCF cathode (1.03 W cm⁻² and 0.53 W cm⁻² at 700 °C).