Oxygen (O2) reduction reaction on Ba-doped LaMnO3 cathodes in solid oxide fuel cells: a density functional theory study

The oxygen adsorption and subsequent reduction on the {100} and {110} surfaces of 25% Ba-doped LaMnO3 (LBM25) have been studied at the density functional theory (DFT) with Hubbard correction and the results compared with adsorption on 25% Ca-doped LaMnO3 (LCM25) and Sr-doped LaMnO3 (LSM25). The trend in the reduction energies at the Mn cation sites are predicted to be in the order LSM25 < LBM25 < LCM25. In addition, the trend in dissociation energies for the most exothermic dissociated precursors follow the order LBM25 < LSM25 < LCM25. The adsorption energies (- 2.14 to - 2.41 eV) calculated for the molecular O-2 precursors at the Mn cation sites of LCM25, LSM25 and LBM25 are thermodynamically stable, when compared directly with the adsorption energies (E-ads = - 0.56 to - 1.67 eV) reported for the stable molecular O-2 precursors on the Pt, Ni, Pd, Cu and Ir {111} surfaces. The predicted Gibbs energies as a function of temperature (T = 500-1100 degrees C) and pressures (p = 0.2 atm) for the adsorption and dissociation on the surfaces were negative, an indication of the feasibility of oxygen reduction reaction on the {100} and {110} surfaces at typical operating temperatures reported in this work.