Platinum-Based Nanoalloys Pt_nTM_55–n (TM = Co, Rh, Au): A Density Functional Theory Investigation

Abstract

Structural and electronic properties of the Pt n TM55–n (TM = Co, Rh, Au) nanoalloys are investigated using density functional theory within the generalized gradient approximation and employing the all-electron projected augmented wave method. For TM = Co and Rh, the excess energy, which measures the relative energy stability of the nanoalloys, is negative for all Pt compositions. We found that the excess energy has similar values for a wide range of Pt compositions, i.e., n = 20–42 and n = 28–42 for Co and Rh, respectively, with the core–shell icosahedron-like configuration (n = 42) being slightly more stable for both Co and Rh systems because of the larger release of the strain energy due to the smaller atomic size of the Co and Rh atoms. For TM = Au, the excess energy is positive for all compositions, except for n = 13, which is energetically favorable due to the formation of the core–shell structure (Pt in the core and Au atoms at the surface). Thus, our calculations confirm that the formation of core–shell structures plays an important role to increase the stability of nanoalloys. The center of gravity of the occupied d-states changes almost linearly as a function of the Pt composition, and hence, based on the d-band model, the magnitude of the adsorption energy of an adsorbate can be tuned by changing the Pt composition. The magnetic moments of Pt n Co55–n decrease almost linearly as a function of the Pt composition; however, the same does not hold for PtRh and PtAu. We found an enhancement of the magnetic moments of PtRh by a few times by increasing Pt composition, which we explain by the compression effects induced by the large size of the Pt atoms compared with the Rh atoms.

Structural formation of binary PtCu clusters: A density functional theory investigation

“…Thus, even for small clusters there is a preferential location for the Pt and Cu atoms, and hence, the formation of core-shell NPs with Cu atoms in the core and Pt atoms in the surface starts at small cluster size. The location of the Pt and Cu atoms are driven by the atomic size and strain release, which has been suggested and confirmed by several studies [2,44,76], i.e., smaller atoms are located in the core region of particles, while larger atoms are located far away from the center of gravity. It occurs mainly for intermediate compositions, i.e., around 50-50%, in which the excess energy is higher.…”

“…For small clusters like those studied in this work, it is not easy to define the core and surface regions as for large TM particles [75,76]. Thus, the RD function is very useful to identify trends in the location of the Pt and Cu atoms.…”

First-principles investigations of the structural, electronic, and magnetic properties of Pt13−nNin clusters

“…In this work, all the first-principles DFT [26,27] calculations are performed in the Vienna Abinitio Simulation Package (VASP) [26,27], with the projector augmented wave method (PAW) pseudopotentials [28]. The density function is treated within the generalized gradient approximation (GGA) [29], using the PerdewBurke-Ernzerhof (PBE) formula [30].…”

Al13@Pt42 Core-Shell Cluster for Oxygen Reduction Reaction

“…Recent DFT calculations show that a core-shell structure plays an important role in increasing the stability of Pt-based nanoalloys, such as Co 13 @Pt 42 and Rh 13 @Pt 42 2526 where Pt shell benefits for the stability of the catalysts under the electrochemical environment2123272829. Thus, we here develop a new core-shell Al 13 @Pt 42 cluster as ORR catalyst, whose surface is assembled with the twelve vertex atoms Pt v and the thirty edge atoms Pt e .…”