Adsorbed methyl (CH3,ad) is a key intermediate in energy-related catalysis over transition metals, e.g., partial oxidation of methane, steam reforming, combustion and selective oxidations of methane and various other hydrocarbons and oxygenates, methanol decomposition. Nickel is an active catalyst ingredient for many methane processing reactions, and Ni(111) is the most common single crystal facet of pure nickel and therefore the most widely studied surface in nickel-related catalysis. Thus, it is crucial to understand the energetics of adsorbed methyl on the Ni(111) surface. Herein, we report a direct measurement of standard enthalpy of formation of CH3,ad on Ni(111) by adsorption calorimetry of the dissociative adsorption of methyl iodide. Experiments were performed at 100 K and 160 K from low to saturated coverages. The bonding energy between CH3,ad and the Ni(111) surface was derived from the resulting heats. Comparison will be made to similar measurements on Pt(111). These results will be useful in understanding and predicting the thermodynamics and activation energies of various elementary reaction steps over Ni and Pt catalysts, and will serve as important benchmark to compare to theoretical calculations (e.g., DFT) to help development of improved computational approaches. Work supported by the National Science Foundation, Chemical Sciences Division under SusChEM grant #CHE-1361939

Energetics of adsorbed methyl on Ni(111) by microcalorimetry

251st National Meeting (2016)

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