Insights into the adsorption and decomposition mechanisms of tar typical model compounds (benzene, toluene and phenol) on Ni(111) surface by DFT calculations

Abstract

Studying the adsorption and decomposition of tar-typical model compounds on nickel surfaces is necessary to guide catalyst design. This study investigates the adsorption and decomposition mechanisms of three typical tar model compounds (benzene-benzene ring without branched chain, toluene-benzene ring with methyl group and phenol-benzene ring with hydroxyl group) on the Ni(111) surface using density functional theory calculations. The results showed that the most stable adsorption site was Bridge0 for benzene and Bridge0-F for toluene and phenol. The adsorption energies were −0.89 eV, −0.76 eV and −0.71 eV, respectively. During decomposition, benzene will first be dehydrogenated (energy barrier of 1.57 eV) and the benzene ring will be opened after the removal of the first H atom (2.10 eV). The rate-limiting step in benzene decomposition is the first dehydrogenation step (1.57 eV). Toluene decomposes like phenol by dehydrogenating functional groups before breaking the benzene ring. The rate-limiting step in the decomposition of toluene is the ring opening of the benzene ring (1.67 eV). The dehydrogenation of the benzene ring is the rate-limiting step in the decomposition of phenol (1.74 eV). This occurs after the removal of the hydrogen atom from the hydroxyl group.