First-principles study of nickel reactivity under two-dimensional cover: Ni2C formation at rotated graphene/Ni(111) interface

Srdjan Stavrić, Simone del Puppo, Željko Šljivančanin, and Maria Peressi
Phys. Rev. Materials 5, 014003 – Published 19 January 2021

Abstract

Recent experiments indicate that the reactivity of metal surfaces changes profoundly when they are covered with two-dimensional (2D) materials. Nickel, the widespread catalyst choice for graphene (G) growth, exhibits complex surface restructuring even after the G sheet is fully grown. In particular, due to excess carbon segregation from bulk nickel to surface upon cooling, a nickel carbide (Ni2C) phase is detected under rotated graphene (RG) but not under epitaxial graphene (EG). Motivated by this experimental evidence, we construct different G/Ni(111) interface models accounting for the two types of G domains. Then, by applying density functional theory, we illuminate the microscopic mechanisms governing the structural changes of nickel surface induced by carbon segregation. A high concentration of subsurface carbon reduces the structural stability of Ni(111) surface and gives rise to the formation of thermodynamically advantageous Ni2C monolayer. We show the restructuring of the nickel surface under RG cover and reveal the essential role of G rotation in enabling high density of favorable C binding sites in the Ni(111) subsurface. As opposed to RG, the EG cover locks the majority of favorable C binding sites preventing the build-up of subsurface carbon density to a phase transition threshold. Therefore we confirm that the conversion of C-rich Ni surface to Ni2C takes place exclusively under RG cover, in line with the strong experimental evidence.

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  • Received 22 October 2020
  • Accepted 24 December 2020

DOI:https://doi.org/10.1103/PhysRevMaterials.5.014003

©2021 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Srdjan Stavrić1,2,*, Simone del Puppo1, Željko Šljivančanin2, and Maria Peressi1

  • 1Physics Department, University of Trieste, via A. Valerio 2, Trieste 34127, Italy
  • 2Vinča Institute of Nuclear Sciences - National Institute of the Republic of Serbia, University of Belgrade, P. O. Box 522, RS-11001 Belgrade, Serbia

  • *sstavric@units.it

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Vol. 5, Iss. 1 — January 2021

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