Ethylene TPD analysis. For selective alkane dehydrogenation, the desired product is the alkene, and to avoid coking, it is critical that the nascent alkene product desorbs from the catalyst, rather than undergoing further dehydrogenation that ultimately results in carbon deposition. At the same time, it is desirable that the binding energy of the alkene on the catalyst be high because it should lower the barrier for the alkane-to-alkene reaction. To probe the branching between alkene desorption vs. unwanted dehydrogenation/coking, we have adopted the strategy of adsorbing ethylene on the catalyst at low temperature, then measuring, using temperature-programmed desorption (TPD), the branching between desorption of intact ethylene, vs. hydrogen desorption, which signals dehydrogenation and carbon deposition. To directly examine the propensity toward carbon deposition, we have also measured the C 1s XPS intensities after multiple ethylene adsorption/desorption cycles.