Understanding the surface segregation behavior of transition metals on Ni(111): a first-principles study

Abstract

The surface composition of an alloying system has an important impact on its catalytic and chemical properties. The segregation behavior of 3d, 4d and 5d transition metals on an Ni(111) surface has been investigated by performing first-principles calculations in the framework of density-functional theory with the generalized gradient approximation for the exchange-correlation functional. Our calculated surface segregation energies are in good agreement with the experimental data as well as with previous calculated results. Most importantly, we have made an attempt to correlate the surface segregation behavior with the surface energy difference between the alloying (solute) metal and the host metal, the elastic energy release, and the heat of solution of the alloying metal in the host metal. By doing so, we not only overcome the difficulties that empirical models encounter, but also clearly identify the importance of each contribution to the segregation behavior of an alloying metal. The present study provides valuable insight into the surface segregation behavior of solute atoms in alloying systems.

N‐Doped Graphene Supported on Metal‐Iron Carbide as a Catalyst for the Oxygen Reduction Reaction: Density Functional Theory Study

“…According to our calculations, Δ of Co, Ni, Cu, and Zn is more negative than that of Fe, which implies that these metal atoms are all energetically favorable to form as a single layer on the Fe 3 C surface (Table S2). In our case, the atomic size difference between the substituted metal atom and the Fe atom can influence the segregation . If the substituted metal atoms are in the second layer of the Fe 3 C substrate, the atomic size difference between the substituted metal and Fe increases strain in the bulk structure, and to relieve the strain, the introduced metal atoms in the bulk exchange with Fe atoms at the surface .…”

“…Stable heterostructures with Cu and Zn atoms are likelyt o form only with Cu or Zn atomsa tt he interface, unlike Ni and Co substitution. This can be relatedt ot he segregationt hat is relatedc losely to the surface energy [40,41] and atomic radius. [41] According to our calculations, DE int of Co, Ni, Cu, and Zn is more negative than that of Fe, which implies that these metal atoms are all energeticallyf avorable to form as as ingle layer ChemSusChem 2020ChemSusChem , 13,996 -1005 www.chemsuschem.org on the Fe 3 Cs urface (Table S2).…”

“…In our case, the atomics ized ifferenceb etween the substituted metal atom and the Fe atom can influence the segregation. [41,42] If the substituted metal atoms are in the second layer of the Fe 3 Cs ubstrate, the atomic size difference between the substituted metal and Fe increases strain in the bulk structure, and to relieve the strain,t he introduced metal atoms in the bulk exchange with Fe atomsa tt he surface. [41][42][43] The atomic size differenceb etween the substituted metal atom and Fe atom in the case of Cu and Zn is relatively larger than that of Ni and Co (atomicr adius = 1.26, 1.25, 1.25, 1.29, and 1.38 for Fe, Co, Ni, Cu, and Zn, respectively [44] ), which leads to al argers train and driving force for Cu and Zn atoms to segregate towardt he Fe 3 Cs urfacec ompared to Ni and Co atoms.I nt he calculations, we also find that Cu and Zn have am ore positive value of DE exc than Ni and Co, whichd escribes the easier surfaces egregation of Cu and Zn toward the Fe 3 Csurface than Ni and Co atoms.…”

Electrodeposited NiRh alloy as an efficient low‐precious metal catalyst for alkaline hydrogen oxidation reaction

“…26,28,60 Since Rh has a lower HBE value than Ni, 61 the presence of Rh in the alloy may decrease the adsorption energy of hydrogen on the catalyst surface and increase the HOR activity. The calculated values of surface segregation energy 62 indicated that Rh tends to segregate toward the surface of alloyed Ni (111). In addition to the modulation of the HBE by alloying, the intrinsic high activity of Rh ( Figure 3A), partially segregated on the surface, is beneficial for the HOR activity of the NiRh alloy catalyst.…”

Theoretical study of B segregation in Mo(110)

“…In previous study, Yu et al [46] investigated Mo segregation in MoNi(111) system using DFT, and found Mo atom prefer to stay in second layer. In addition, another work of them considered some transition metals segregation in Ni(111) surface such as W, Mo, V, Fe, Cr [47]. These elements prefer to occupy a site in the second layer.…”