arXiv subjects

Valentina Tozzini

Publications and source records attributed to Valentina Tozzini.

22 records · Page 2Linked to original sources

arXiv2012

Prospects for hydrogen storage in graphene

Hydrogen-based fuel cells are promising solutions for the efficient and clean delivery of electricity. Since hydrogen is an energy carrier, a key step for the development of a reliable hydrogen-based technology requires solving the issue of storage and transport of hydrogen. Several proposals based on the design of advanced materials such as metal hydrides and carbon structures have been made to overcome the limitations of the conventional solution of compressing or liquefying hydrogen in tanks. Nevertheless none of these systems are currently offering the required performances in terms of hydrogen storage capacity and control of adsorption/desorption processes. Therefore the problem of hydrogen storage remains so far unsolved and it continues to represent a significant bottleneck to the advancement and proliferation of fuel cell and hydrogen technologies. Recently, however, several studies on graphene, the one-atom-thick membrane of carbon atoms packed in a honeycomb lattice, have highlighted the potentialities of this material for hydrogen storage and raise new hopes for the development of an efficient solid-state hydrogen storage device. Here we review on-going efforts and studies on functionalized and nanostructured graphene for hydrogen storage and suggest possible developments for efficient storage/release of hydrogen at ambient conditions.

cond-mat.mes-hall↗

arXiv2011

Reversible hydrogen storage by controlled buckling of graphene layers

We propose a multi-layer graphene-based device in which storage and release of atomic hydrogen is obtained by exploiting and controlling the corrugation of the layers. The proposal is based on density-functional simulations of hydrogen chemisorption on graphene with superimposed corrugation. We report a tunability of the binding energies of more than 2 eV by changing the sheet out-of-plane deformation up to \pm 0.2 Å, the convex regions allocating the energetically favored hydrogen binding sites. We discuss an optimized process of curvature inversion that can lead to efficient and fast hydrogen release and H2 formation. Our corrugated graphene device can potentially reach gravimetric capacities of ~8 wt % and reversibly store and release atomic hydrogen by application of external fields without the need of modifying temperature and pressure.

cond-mat.mes-hall↗

arXiv2009

Electronic structure and Peierls instability in graphene nanoribbons sculpted in graphane

Graphene nanoribbons are semiconductor nanostructures with great potentials in nanoelectronics. Their realization particularly with small lateral dimensions below a few nanometers, however, remains challenging. Here we theoretically analyze zig-zag graphene nanoribbons created in a graphane substrate (a fully saturated two-dimensional hydrocarbon with formula CH) and predict that they are stable down to the limit of a single carbon chain. We exploit density functional theory with B3LYP functional that accurately treats exchange and correlation effects and demonstrate that at small widths below a few chains these zig-zag nanoribbons are semiconducting due to the Peierls instability similar to the case of polyacetylene. Graphene nanoribbons in graphane might represent a viable strategy for the realization of ultra-narrow semiconducting graphene nanoribbons with regular edges and controlled chemical termination and open the way for the exploration of the competition between Peierls distortion and spin effects in artificial one-dimensional carbon structures.

cond-mat.mes-hall↗

arXiv2001

The coherent dynamics of photoexcited green fluorescent proteins

The coherent dynamics of vibronic wave packets in the green fluorescent protein is reported. At room temperature the non-stationary dynamics following impulsive photoexcitation displays an oscillating optical transmissivity pattern with components at 67 fs (497 cm-1) and 59 fs (593 cm-1). Our results are complemented by ab initio calculations of the vibrational spectrum of the chromophore. This analysis shows the interplay between the dynamics of the aminoacidic structure and the electronic excitation in the primary optical events of green fluorescent proteins.

physics.bio-ph↗