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We utilize density functional theory to explore hydrogen mobility on doped graphene surfaces, and identify candidate materials that will meet both thermodynamic and kinetic constraints for room temperature hydrogen uptake via surface diffusion from a catalyst that dissociates molecular H2 into active surface species.[1]  The results help to explain recent spectroscopic evidence of reversible ambient temperature hydrogenation of oxidized carbon surfaces via hydrogen spillover from platinum nanoparticles[2] and clarify the hydrogen spillover mechanism. The identified kinetic and thermodynamic constraints demonstrate that significant mobility at room temperature will occur only via H diffusion in a chemisorbed state, and this requires heteroatoms or chemical dopants to simultaneously increase the binding energy and decrease the barrier for chemical diffusion. Despite prior assumptions in the literature, the binding energy of atomic hydrogen on a surface is not correlated to mobility when the surface does not directly dissociate the H2.  Beyond hydrogen storage, clarification of the mechanism by which hydrogen diffuses on carbon extends to basic surface science, catalysis, astrophysics, novel materials, energy storage devices, and electronics.  

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1.            Lueking, A.D., G. Psofogiannakis, and G.E. Froudakis, Atomic Hydrogen Diffusion on Doped and Chemically Modified Graphene. Journal of Physical Chemistry C, 117 (12), pp 6312-6319, 2013. http://pubs.acs.org/doi/abs/10.1021/jp4007763

2.            Liu, X.M., et al., Evidence for Ambient-Temperature Reversible Hydrogenation in Pt-doped Carbons. Nano Letters, 2013. 13: p. 137-141. http://pubs.acs.org/doi/abs/10.1021/nl303673z

 

Press Release, RE: Nano Letter study

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