On the Effects of Doping on the Catalytic Performance of (La,Sr)CoO3. A DFT Study of CO Oxidation

The effects of modifying the composition of LaCoO3 on the catalytic activity are predicted by density functional calculations. Partially replacing La by Sr ions has benefical effects, causing a lowering of the formation energy of O vacancies. In contrast to that, doping at the Co site is less effective, as only 3d impurities heavier than Co are able to stabilize vacancies at high concentrations. The comparison of the energy profiles for CO oxidation of undoped and of Ni-, Cu-m and Zn-doped (La,Sr)CoO3(100) surface shows that Cu is most effective. However, the effects are less spectacular than in the SrTiO3 case, due to the different energetics for the formation of oxygen vacancies in the two hosts.

Influence of Magnetism on Interaction Energy between 3d Impurities and Hydrogen in Palladium Crystal in the Presence of Vacancies

In this paper we have studied from first-principles the effect of magnetism on the hydrogen-metal interaction and the binding properties of palladium with 3d-alloying atoms in the presence of vacancies induced during hydrogenation process. Our first-principles calculations were carried out by means of state of the art ab-initio method based on density functional theory and all-electron PAW-potentials. We have analyzed the changes of the atomic and electronic structures of palladium crystal induced by the presence of substitutional 3d-alloying atoms, interstitial hydrogen and structural defect (palladium vacancy). The obtained results have shown that magnetism can strongly affect the hydrogen-metal interaction in palladium based alloys. We have also demonstrated that the presence of vacancies in the palladium matrix can alter the interaction energy between hydrogen and alloying transition metal atoms.