Plasma-enhanced catalysis offers a new approach for efficiently achieving efficient catalytic conversion for chemicals and fuels that traditional have required high temperatures and high pressures. Exemplary applications include ammonia synthesis, dry methane reforming, and methane conversion. A unique feature of plasma-enhanced catalysis compared to thermal catalysis is the presence of reactive hydrogen radicals and ions in the gas phase above the catalyst surface. In exploring reaction mechanisms for plasma-enhanced catalysis, we have included in our studies some UHV surface science studies of model single crystal metal surfaces, focusing on the interactions of incident energetic hydrogen atoms and ions with metal surfaces, with and without adsorbates present.  In particular, we describe here recent measurements of the formation and thermal stability of subsurface hydrogen using a Ni(110) surface, and the unique hydrogenation reactions of CO adsorbed on Ni(110) that occur with energetic hydrogen. We demonstrate experimentally the production of methanol and formaldehyde from CO hydrogenation on Ni(110) and confirm the role of subsurface hydrogen in the mechanism of these reactions. These results, when combined with theoretical studies, show that Eley−Rideal or hot-atom mechanisms are not as important under these conditions, and thus thermal reactions involving subsurface hydrogen are the primary reaction mechanisms leading to methanol from CO hydrogenation on a Ni(110) surface. Such information will be helpful for a fuller understanding of the role of subsurface hydrogen and its reactivity in hydrogenation reactions in plasma-enhanced catalysis over Ni-based catalysts.

Formation and thermal stability of subsurface hydrogen and its reactivity for the hydrogenation of CO on Ni(110)

2019 Spring National Meeting

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