Pt Monolayer on Fe(001) Catalyst for O2 Reduction: A First Principles Study

Abstract

The results of spin-polarized density functional theory calculations for O2 dissociative adsorption on Pt monolayer on Fe(001) (PtML/Fe(001)) structure are presented and are compared with that of Pt(001). The potential energy curves for the reaction of Pt with O2 as a function of O2 center-of-mass distance from the platinum layer and O-O interatomic distance show that PtML/Fe(001) produces a combination of lower activation barrier for O2 dissociation and weaker O-atom binding which are both beneficial for a easier O2 dissociation to produce adsorbed O and for subsequent reactions of O with other surface species for O2 reduction process. Local density of states at Pt surface shows induced spin polarization on the Pt atomic layer characterized by dzz peak at the Fermi level, in good agreement with experimental findings. Such effect increases unfilled dzz orbital on Pt surface modifying Pt electronic surface structure towards a favorable O2-Pt d interaction. Decrease in the magnetic moments of O and Pt atoms upon O adsorption indicates an antiparallel O unpaired electron spin alignment with Pt spin rendering consequent stabilization and a lowering of energy cost to O2 activation. On the other hand, the weaker O binding reflects the stronger Pt-Fe interlayer bonding typical for such bimetallic systems. [DOI: 10.1380/ejssnt.2007.117]