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Nano colloquium: K. Kahkiani

Foto: Khatuna Kahkiani (© http://www.rwth-aachen.de)


Pisa - 18.05.2017 - Nano colloquium: K. Kahkiani
Khatuna Kakhiani (NEST, NANO-CNR)
Title: “Manipulating graphene morphology: theory and computer simulations”
Nest seminar room in Pisa, @11.00 am
Graphene’s strength and extreme flexibility allow sustaining ripples in a wide range of amplitudes and wavelengths. This circumstance can be exploited for applications: ripples produce a modulation of the local curvature in a considerable range, which in turn is strongly correlated with the stability of hydrogen chemisorbed atoms[1]. The functionalization of curved graphene with hydrogen, or other adatoms, enables tuning its chemical and adsorption properties for storage applications, as well as capture and purification of gases and mixtures. While atomic hydrogen adhesion is a spontaneous process, with a very small barrier, molecular hydrogen (H2) chemisorption process is characterized by a barrier high on the order of ~1.5ev/atom, making the kinetics of loading very slow. In this work, we show that curvature manipulation could be used to improve the adhesion kinetics of molecular hydrogen on rippled graphene. To this aim, we address the dependence of chemi(de)sorption barriers on curvature via a DFT based study, accounting for the role of dispersion forces. We use model systems with various levels of corrugation generated by lateral compression of the isolated sheet [2], chosen, to approximate the symmetry of natural rippling of graphene grown on SiC[3]. We evaluate the chemi(de)sorption profiles to estimate the levels of curvature needed in a real device.
[1] V Tozzini, V Pellegrini, J Phys Chem C, 115, (2011), 25523.
[2] A Rossi, S Piccinin, V Pellegrini, S de Gironcoli, V Tozzini, J Phys Chem C, 119, (2015), 7900. [3] S Goler, C Coletti, V Tozzini, V Piazza, T Mashoff, F. Beltram, V. Pellegrini, S. Heun J Phys Chem C, 117, (2013), 11506.

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