Oxygen adsorption at La _1-xSr _xMnO ₃(001) surfaces: Predictions from first principles

The interaction of atomic and molecular oxygen with MnO ₂- and La(Sr)O-terminated (001) surfaces of Sr-doped LaMnO ₃ has been studied using the B3LYP hybrid exchange-correlation functional within the framework of density functional theory (DFT). Using the obtained binding energies in conjunction with the ab initio thermodynamics we predict that adsorbed O atoms stabilize the surface of an LSM cathode at typical SOFC working conditions (T=1100 K, pO ₂=0.2 p ₀). The most favorable oxygen adsorption sites have been found to be atop surface Mn atoms on the MnO ₂-terminated surface and on the hollow positions of the La(Sr)O-terminated LSM(001) surface. An O ₂ molecule adsorbed at a hollow position of the La(Sr)O-terminated surface is readily dissociated, which adds a substantial contribution to the ionic transport at the LSM surface.