Carbon-supported Pt catalyst systems containing defect adsorption sites on the anode of direct methanol fuel cells were investigated, to elucidate the mechanisms of H2 dissociation and carbon monoxide (CO) poisoning. Density functional theory calculations were carried out to determine the effect of defect sites located neighboring to or distant from the Pt catalyst on H2 and CO adsorption properties, based on electronic properties such as adsorption energy and electronic band gap. Interestingly, the presence of neighboring defect sites led to a reduction of H2 dissociation and CO poisoning due to atomic Pt filling the defect sites. At distant sites, H2 dissociation was active on Pt, but CO filled the defect sites to form carbon π-π bonds, thus enhancing the oxidation of the carbon surface. It should be noted that defect sites can cause CO poisoning, thereby deactivating the anode gradually.

We investigated the adsorption of Na on graphene and graphene oxide, which are used as anode materials in sodium ion batteries, using density functional theory. The adsorption energy for Na on graphene was -0.507 eV at the hollow sites, implying that adsorption was favorable. In the case of graphene oxide, Na atoms were separately adsorbed on the epoxide and hydroxyl functional groups. The adsorption of Na on graphene oxide-epoxide (adsorption energy of -1.024 eV) was found to be stronger than the adsorption of Na on pristine graphene. However, the adsorption of Na on graphene oxide-hydroxyl resulted in the generation of NaOH as a by-product. Using density of states (DOS) calculations, we found that the DOS of the Na-adsorbed graphene was shifted down more than that of the Na-adsorbed graphene oxide-epoxide. In addition, the intensity of the DOS around the Fermi level for the Na-adsorbed graphene was higher than that for the Na-adsorbed graphene oxide-epoxide.