Theoretical study of selective hydrogenation in a mixture of acetylene and ethylene over Fe@W(1 1 1) bimetallic surfaces

The selectivity of formation of ethylene from the hydrogenation of acetylene is tunable to 100% on our designed catalytic surface, Fe(1,2)@W(1 1 1), of which the first two layers of a W(1 1 1) surface are replaced by Fe atoms. Three possible reaction paths for the hydrogenation of acetylene on these metal surfaces are solely formation of ethylene followed by desorption from the surface, complete hydrogenation to ethane, and decomposition to two methylene fragments. The tested monometallic and bimetallic surfaces were W(1 1 1), Fe(1)@W(1 1 1), Fe(1,2)@W(1 1 1), Fe(1 1 1), W(1)@Fe(1 1 1) and W(1,2)@Fe(1 1 1); Fe(1)@W(1 1 1) represents the first layer of tungsten (1 1 1) surface being replaced by the iron atoms, and vice versa on a W(1)@Fe(1 1 1) surface. On a Fe(1,2)@W(1 1 1) surface, the barrier to form ethylene is only 0.84 eV, the least of all specified surfaces. The barrier to further hydrogenation to C ₂H₅ is 2.43 eV, whereas that of CC bond scission is 2.27 eV; the latter two barriers are much greater than that, 0.42 eV, for desorption of C₂H₄. Ethylene could hence be the sole and final product to be desorbed from a catalytically tuned Fe(1,2)@W(1 1 1) surface in the hydrogenation of acetylene.