Dpto. Física Teórica, Atómica y Óptica - Capítulos de monografías https://uvadoc.uva.es/handle/10324/1311 2026-04-12T04:03:35Z 2026-04-12T04:03:35Z Alonso Martín, Julio Alfonso López Santodomingo, María José https://uvadoc.uva.es/handle/10324/36036 2021-06-23T10:25:02Z 2018-01-01T00:00:00Z

Hydrogen is viewed as a possible alternative to the fossil fuels in transportation. The technology of fuel-cell engines is fully developed, and the outstanding remaining problem is the storage of hydrogen in the vehicle. Porous materials, in which hydrogen is adsorbed on the pore walls, and in particular nanoporous carbons, have been investigated as potential onboard containers. Furthermore, metallic nanoparticles embedded in porous carbons catalyze the dissociation of hydrogen in the anode of the fuel cells. For these reasons the interaction of hydrogen with the surfaces of carbon materials is a topic of high technological interest. Computational modeling and the density functional formalism (DFT) are helping in the task of discovering the basic mechanisms of the interaction of hydrogen with clean and doped carbon surfaces. Planar and curved graphene provide good models for the walls of porous carbons. We first review work on the interaction of molecular and atomic hydrogen with graphene and graphene nanoribbons, and next we address the effects due to the presence of metal clusters on the surface because of the evidence of their role in enhancing hydrogen storage.

2018-01-01T00:00:00Z Alonso, Lydia Alonso Martín, Julio Alfonso López Santodomingo, María José https://uvadoc.uva.es/handle/10324/29154 2022-03-29T12:07:55Z 2018-01-01T00:00:00Z

The most stable form of solid carbon is graphite, a stacking of graphene 2 layers in which the carbon atoms show sp2 hybridization which leads to strong intra3 layer bonding. Diamond is a denser phase, obtained at high pressure. In diamond the 4 carbon atoms show sp3 hybridization. Metastable solid carbon phases can be pre5 pared also with lower density than graphite (in fact, densities lower than water); for 6 instance the carbide-derived carbons. These are porous materials with a quite disor7 dered structure. Atomistic computer simulations of carbide-derived carbons indicate 8 that the pore walls can be viewed as curved and planar nanographene ribbons with 9 numerous defects and open edges. Consequently, the hybridization of the carbon 10 atoms in the porous carbons is sp2. Because of the high porosity and large specific 11 surface area, nanoporous carbons find applications in gas adsorption, batteries and 12 nanocatalysis, among others. We have performed computer simulations, employing 13 large simulation cells and long simulation times, to reveal the details of the structure 14 of the nanoporous carbons. In the dynamical simulations the interactions between 15 the atoms are represented by empirical many-body potentials. We have also investi16 gated the effect of the density on the structure of the disordered carbons and on the 17 hybridization of the carbon atoms. At low densities, typical of the porous carbide18 derived carbons formed experimentally, the hybridization is sp2. On the other hand, 19 as the density of the disordered material increases, a growing fraction of atoms with 20 sp3 hybridization appears

2018-01-01T00:00:00Z Molina Martín, Luis Miguel https://uvadoc.uva.es/handle/10324/29151 2021-12-03T09:08:53Z 2017-01-01T00:00:00Z

The formation of self-assembled surface structures based on hydrogen bonding is ones of the most active research areas in surface science. This article discusses, mostly from a theoretical point of view, the fundamental aspects of hydrogen bonding interaction and their relationship to the formation of ordered hydrogenbonded networks on surfaces. First, the basic theoretical concepts about hydrogen bonding and its modelization are presented, outlining the large variety of techniques available for the study of these systems. Second, some relevant research results on this field are reviewed and discussed, describing two important main situations: on one hand, the adsorption of water on both metallic and oxide surfaces; on the other, the formation of ordered networks of hydrogenbonded organic molecules on various types of surfaces. In the latter case, two main situations are described, involving or not a relevant role of the surface in the formed superstructures.

2017-01-01T00:00:00Z