New insights into designing metallacarborane based room temperature hydrogen storage media

Abstract

Metallacarboranes are promising towards realizing room temperature hydrogen storage media because of the presence of both transition metal and carbon atoms. In metallacarborane clusters, the transition metal adsorbs hydrogen molecules and carbon can link these clusters to form metal organic framework, which can serve as a complete storage medium. Using first principles density functional calculations, we chalk out the underlying principles of designing an efficient metallacarborane based hydrogen storage media. The storage capacity of hydrogen depends upon the number of available transition metal d-orbitals, number of carbons, and dopant atoms in the cluster. These factors control the amount of charge transfer from metal to the cluster, thereby affecting the number of adsorbed hydrogen molecules. This correlation between the charge transfer and storage capacity is general in nature, and can be applied to designing efficient hydrogen storage systems. Following this strategy, a search for the best metallacarborane was carried out in which Sc based monocarborane was found to be the most promising H2 sorbent material with a 9 wt.% of reversible storage at ambient pressure and temperature.

Low oxygen levels contribute to improve photohydrogen production in mixotrophic non-stressed Chlamydomonas cultures

“…However, this may lead the production of highly diluted H 2 , which may in turn reduce the potential for commercial applications. Utilization of bioreactors covered with materials, such as metallacarboranes, with high reversible capacity for binding H 2 at low temperatures [ 30 ] might be a way to avoid H 2 uptake.…”

Carboranes in the chemist's toolbox

“…A theoretical study restricted to metallacarboranes, which included 7-vertex M(C 2 B 4 H 6 ) and 14-vertex M 2 (C 4 B 8 H 12 ) as well as 12-vertex M(C 2 B 9 H 11 ) and M 2 (C 2 B 8 H 11 ) systems, found that metallacarborane-based MOFs are excellent candidates for hydrogen storage, with a capacity of up to five H 2 molecules per transition metal atom; scandium and titanium are predicted to have the highest capacity (∼8 wt%). 137 Other theoretical investigations, on titanium sandwiches with planar C 3 B 2 H 5 rings, 138 Li and Na complexes with planar C 4 B 2 H 6 rings, 139 and scandium-carborane complexes, 140 "paddlewheel" nodes, three architecturally distinct MOFs were obtained, one of which is depicted in Fig. 25.…”

Remarkable enhancement in hydrogen storage on free-standing Ti 3 B and BC 3 supported Ti 3 clusters

“…1(b). The inclusion of boron in the Ti cluster enhances the charge depletion near the Ti atoms, rendering more d-orbitals available for H 2 adsorption [49]. This charge depletion is most in the case of Ti 2 B and continues to reduce systematically in the next four clusters (Ti 3 B > Ti 4 B > Ti 5 B > Ti 6 B).…”