CO and H Adsorption on Pt/WC(0001) Surface

Density functional theory (DFT) calculations and periodic slab models were used to investigate the geometrical structures and surface energies of two different WC(0001) surfaces. The adhesion energies and separation work of Pt monolayer adhesion on the two WC(0001) surfaces at high-symmetry sites were calculated. Results show that the W-terminated WC(0001) is favored and that the W-terminated surface with Pt monolayer adhesion at the hcp site is the most stable Pt-ML/WC(0001) structure. On the basis of the above results, the adsorption behavior of the CO molecule and hydrogen atom on the Pt-ML/WC(0001) surface was compared with those obtained on the Pt(111) surface with a surface structure similar to the Pt-ML/WC(0001) surface. At a low coverage of 0.25 ML (monolayer), an obvious elongation of the Pt-C distance and a decrease in CO adsorption energy show that the Pt-ML/WC(0001) surface, relative to the Pt(111) surface, exhibits much improved resistance to CO poisoning. The density of states further explains the bonding mechanism of CO and Pt atoms on different surfaces. At the same coverage, the maximum hydrogen adsorption energy on the Pt-ML/WC(0001) surface is equal to or even slightly higher than that on the Pt(111) surface. This suggests that Pt/WC possesses good catalytic activity during the hydrogen oxidation reaction and is a promising alternative anode catalyst for proton exchange membrane fuel cells (PEMFC).