The reversible hydrogenation-dehydrogenation of membrane and epitaxial graphenes

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Results of thermodynamic analysis of some theoretical and experimental (TDS, STM, STS, HREELS/LEED, PES, ARPS, Raman spectroscopy and others) data on the so called reversible hydrogenation and dehydrogenation of membrane and epitaxial graphenes are presented. In the framework of the formal kinetics approximation of the first order rate reaction, some thermodynamic quantities for the reaction of hydrogen sorption (the reaction rate constant, the reaction activation energy, the per-exponential factor of the reaction rate constant) have been determined and compared with the theoretical ones. Some models and characteristics of hydrogen chemisorption on graphite (on the basal and edge planes) have been used for interpretation of results of the data treatment and comparison, with the aim of revealing the atomic mechanisms of hydrogenation and dehydrogenation of epitaxial graphenes and their difference from the mechanisms for membrane graphenes. The cases of both a non-diffusion rate limiting kinetics and a diffusion rate limiting kinetics are considered.