A comprehensive study of
acetylene adsorption on δ-MoC(001),
TiC(001) and ZrC(001) surfaces was carried out by means of calculations based on periodic density functional theory, using the Perdew-Burke-Ernzerhof exchange-correlation functional. It was found that the bonding of
acetylene was significantly affected by the electronic and structural properties of the carbide surfaces. The adsorbate interacted with
metal and/or
carbon sites of the carbide. The interaction of
acetylene with the
TiC(001) and ZrC(001) surfaces was strong (binding energies higher than -3.5 eV), while moderate
acetylene adsorption energies were observed on δ-MoC(001) (-1.78 eV to -0.66 eV). Adsorption energies, charge density difference plots and Mulliken charges suggested that the binding of the
hydrocarbon to the surface had both ionic and covalent contributions. According to the C-C bond lengths obtained, the adsorbed molecule was modified from
acetylene-like into
ethylene-like on the δ-MoC(001) surface (desired behavior for hydrogenation reactions) but into
ethane-like on
TiC(001) and ZrC(001). The obtained results suggest that the δ-MoC(001) surface is expected to have the best performance in selective hydrogenation reactions to convert
alkynes into
alkenes. Another advantage of δ-MoC(001) is that, after C2H2 adsorption, surface
carbon sites remain available, which are necessary for H2 dissociation. However, these sites were occupied when C2H2 was adsorbed on
TiC(001) and ZrC(001), limiting their application in the hydrogenation of
alkynes.