Enhanced CO tolerance of Pt clusters supported on graphene with lattice vacancies

Abstract

The adsorption of CO on Pt4 clusters supported on graphene with lattice vacancies is studied theoretically using the first-principles calculation. Our results show that the electronic structure of the graphene-supported Pt4 clusters is significantly modified by the interaction with carbon dangling bonds. As a result the adsorption energy of CO at a Pt site decreases almost linearly with the lowering of the Pt d-band center, in analogy with the linear law previously reported for CO adsorption on various Pt surfaces. An exceptional behavior is found for Pt4 supported on graphene with a tetravacancy, where CO adsorption is noticeably weaker than predicted by the shift in the d-band center. Detailed electronic structure analyses reveal that the deviation from the linear scaling can be attributed to lack of Pt d states near the Fermi level that hybridize with CO molecular orbitals. The weakening of CO adsorption on the Pt4 clusters is considered as a manifestation of the support effect of graphene, and leads to the enhancement of CO poisoning tolerance that is crucial for developing high-performance Pt cluster catalysts.