Theoretical insights on the effect of alloying with Co in the mechanism of graphene growth on a Cu[sbnd]Co (1 1 1) catalyst

Abstract

Alloying Cu catalyst with transition metals with high C solubility is an effective technique for growing graphene with a precisely controlled number of layers. Co is a transition metal with high C solubility and is suitable for alloying with Cu catalysts due to its similar atomic size. In this study, we elucidate the mechanism of graphene growth on a CuCo(111) catalyst by evaluating the energetics, thermodynamics, and kinetics of potential C source species, CHi (i = 0, 1, 2, 3), using a first-principles method. Alloying Cu with Co atoms upshifts the d-band center, which induces a robust p-d hybridization between the CuCo(111) catalyst and the C source species. From relative population calculations, it is found that the C monomer on the catalyst subsurface always becomes dominant in the range of growth conditions studied. Therefore, the C monomer in the catalyst subsurface controls the segregation growth mechanism. In addition, it is found that the diffusion of C monomer into the CuCo(111) catalyst subsurface is an exothermic process with a low activation energy. These results enable us to suggest a novel alternating alloy catalyst for growing few-layer graphene with a precisely controlled number of layers.