A computational study of H 2 dissociation and CO adsorption on the Pt ML/WC(0 0 0 1) surface

Abstract

We studied computationally the relative stability of Pt ML/WC(0 0 0 1) [pseudomorphic monolayer of Pt(1 1 1) on WC(0 0 0 1)] interfacial structures using a density functional slab model approach. The work of adhesion was calculated for six different interfacial structures, taking into account both W- and C-terminations of the carbide. The results show that the optimal interfacial structure of Pt ML/WC(0 0 0 1) is the W-terminated WC(0 0 0 1) with Pt atoms adhesion on the hcp site (W-hcp). The nature of metal/carbide bonding for the W-hcp interfacial geometry was determined on the basis of the partial density of states (PDOS). Adsorption of atomic hydrogen and dissociation of the hydrogen molecule on the W-hcp Pt ML/WC(0 0 0 1) was investigated and compared to that on Pt(1 1 1). It is found that the most favorable H 2 dissociation channels need similar activation energies of 5.28 and 4.93 kJ/mol on Pt ML/WC(0 0 0 1) and Pt(1 1 1), respectively, with the release of considerable reaction energies. Furthermore, adsorption of CO on the W-hcp Pt ML/WC(0 0 0 1) and Pt(1 1 1) was also investigated. The results indicate that Pt ML/WC(0 0 0 1) is much less susceptible to CO poisoning than Pt(1 1 1), especially at the low coverage of CO.