The interaction of noble metal with La_1-xSr _xMnO₃ (001) surface and catalytic role for oxygen adsorption: A density functional theory study

Adsorption mechanisms of noble metals (Ag, Pd, Pt) on MnO ₂-terminated (001) surface and their catalytic role for oxygen adsorption have been investigated using the first-principles density functional theory calculations. The analysis of the adsorption energies reveals that the energetically favorable configuration for Ag and Pd adsorption is at the O site, whereas one for Pt adsorption is at the Mn site. Pt atom exhibits the largest adsorption energy, followed by Pd and Ag atoms. Both bond population and PDOS (partial density of states) analysis confirm the formation of adatom-O-Mn bonds. Adsorption is accompanied by a charge transfer between adatoms and surface atoms. Significantly, we predict that the order on the increase of O₂ adsorption energy follows the Pd > Ag > Pt due to pre-adsorbed noble metal atoms. The calculated bond length and bond population of O₂ molecule demonstrate that pre-adsorbed noble metal atoms facilitates O ₂ molecule dissociate to O atoms, thus contributing to the surface oxygen diffusion process. Our calculations identify an important catalytic role of noble metal in LSM-based catalysts, which may improve electrochemical performance for SOFCs cathodes.