Xingli Chu

Density functional study on the mechanism for the highly active palladium monolayer supported on titanium carbide for the oxygen reduction reaction.

The adsorption, diffusion, and dissociation of O2 on the palladium monolayer supported on TiC(001) surface, MLPd/TiC(001), are investigated using ab initio density functional theory calculations. Strong adhesion of palladium monolayer to the TiC(001) support, accompanied by a modification of electronic structure of the supported palladium, is evidenced. Compared with Pt(111) surface, the MLPd/TiC(001) can enhance the adsorption of O2, leading to comparable dissociation barrier and a smaller diffusion barrier of O2. Whilst the adsorption strength of atomic O (the dissociation product of O2) on MLPd/TiC(001) is similar to that on the Pt(111) surface, possessing high mobility, our theoretical results indicate that MLPd/TiC(001) may serve as a good catalyst for the oxygen reduction reaction.

Interactions of small platinum clusters with the TiC(001) surface

Density functional theory calculations are used to elucidate the interactions of small platinum clusters (Ptn, n = 1–5) with the TiC(001) surface. The results are analyzed in terms of geometric, energetic, and electronic properties. It is found that a single Pt atom prefers to be adsorbed at the C-top site, while a Pt2 cluster prefers dimerization and a Pt3 cluster forms a linear structure on the TiC(001). As for the Pt4 cluster, the three-dimensional distorted tetrahedral structure and the two-dimensional square structure almost have equal stability. In contrast with the two-dimensional isolated Pt5 cluster, the adsorbed Pt5 cluster prefers a three-dimensional structure on TiC(001). Substantial charge transfer takes place from TiC(001) surface to the adsorbed Ptn clusters, resulting in the negatively charged Ptn clusters. At last, the d-band centers of the absorbed Pt atoms and their implications in the catalytic activity are discussed.