To quantify the effect of changes in electronic structure on catalytic behavior, 4 shows our previously reported reaction barriers for ethane (Figure ) and ethylene (Figure (c)) plotted in the same style as in Figure . There is an increase in the ethane C-H activation barrier upon the deposition of C 2 , to 0.53 eV but this increase is less than in the absence of Ge, in Figure , where the barrier increased to 0.64 eV. Thus, doping with Ge allows the cluster to remain more active for ethane C-H activation after partial coking. Ge strengthens π bonding in the C 2 unit which would have to be broken to bind additional coke, so the combined electronic effects of Ge and C 2 hinder further coking. This manifests in different binding energies of ethylene to Pt 4 C 2 (-1.85 eV) and Pt 4 GeC 2 (-2.10 eV), for structures where ethylene binds directly to the C 2 unit in the cluster (Figures and).