Correlating electronic properties of bimetallic surfaces with reaction pathways of C2 hydrocarbons.

The rate and selectivity of chemical reactions on transition-metal surfaces can be controlled by using different bimetallic combinations. The interaction of bimetallic components leads to a change in the electronic properties of the surface, which in turn produces a change in chemical reactivity. In the current paper, we illustrate the correlation of the electronic properties of bimetallic surfaces with the reaction pathways of C2 hydrocarbons. Density functional theory (DFT) was used to study the binding of hydrogen, ethylene, acetylene, ethyl, and vinyl on monometallic and bimetallic transition-metal surfaces. The binding energies of these species were found to correlate with the d-band centers of these surfaces. The binding energies for hydrogen atoms on bimetallic surfaces were lower than for those on the corresponding parent metal surfaces. This trend was consistent for ethylene and acetylene binding. Comparative studies between acetylene and ethylene revealed that acetylene was more strongly bonded to the monometallic and the bimetallic surfaces than was ethylene. Bond order conservation (BOC) theory was used to calculate the activation barriers for ethyl dehydrogenation to ethylene and vinyl dehydrogenation to acetylene. The activation barriers for these reactions were correlated with the surface d-band center of the substrates.