• Tripkovic, Vladimir
• Durante, Christian
• Rossmeisl, Jan
• Zheng, Jian
• Granozzi, Gaetano
• Marega, Carla
• Rizzi, Gian Andrea

Abstract

A set of electrochemical and X-ray spectroscopy measurements have been used conjointly with density functional theory (DFT) simulations to study the activity and stability of Pd5Ce for the oxygen reduction reaction. A polycrystalline Pd5Ce rod has been selected as a model catalyst to test if results on a several-fold activity increase of a series of Pt/rare-earth alloys hold also for Pd rare-earth alloys. Pd5Ce crystallizes in two phases, a so-called low-temperature phase, L-Pd5Ce, which has a cubic symmetry, and a high-temperature phase, H-Pd5Ce, with a hexagonal symmetry. In both cases, a several-layers-thick Pd skin forms on the surface. Preliminary DFT results show that Pd overlayers under ≥2% compressive strain should be more active than Pt. In L-Pd5Ce, the overlayer is under tensile strain, whereas in H-Pd5Ce (a structure similar to Pt5Ce), it is under compressive strain. We have confirmed that in our sample, L-Pd5Ce is the dominant phase, both in the bulk and the outermost layers, while a H-Pd5Ce-l...

Topics

• density
• impedance spectroscopy
• surface
• phase
• theory
• simulation
• Oxygen
• density functional theory
• X-ray spectroscopy