Effects of Cu ratios on the C1–C6 growth mechanism on copper–nickel bimetallic surfaces

Abstract

The adsorption and growth mechanisms of C_n (n = 1–6) on different Cu–Ni surfaces are calculated by density functional theory (DFT). The results demonstrate that Cu doping affects the growth mechanism of the deposited carbon on the catalyst surface. Firstly, the addition of Cu weakens the interaction between C_n and the adsorbed surface, which is proved by the results of density of states (DOS) and partial density of states (PDOS). The weakening of the interaction allows C_n to perform at higher proportions of Cu-doped surfaces with a behavior consistent with that in the gas phase. A comparison of the growth energies of the different pathways of C_n in the gas phase shows that the main pathway for the C_n growth is chain-to-chain (CC). The CC reaction is also the main pathway for the growth of C_n on the surfaces, which is enhanced by the doping of Cu. In addition, analysis of the growth energy revealed that C₂–C₃ is the rate-determining step in the growth process of C_n. The doping of Cu enhances the growth energy of this step, contributing to the suppression of the growth of the deposited carbon on the adsorbed surface. Moreover, an average carbon binding energy shows that the doping of Cu on the Ni surface could weaken the structural stability of C_n, favoring the elimination of carbon deposited on the catalyst surface.