Blending materials composed of boron, nitrogen and carbon to transform approaches to liquid hydrogen stores

Abstract

Mixtures of hydrogen storage materials containing the elements of boron, nitrogen, carbon, i.e., isomers of BN cyclopentanes are examined to find a 'fuel blend' that remains a liquid phase throughout hydrogen release, maximizes hydrogen storage density, minimizes impurities and remains thermally stable at ambient temperatures. We find that the mixture of ammonia borane dissolved in 3-methyl-1,2-dihydro-1,2-azaborolidine (compound B) provide a balance of these properties and provides ca. 5.6 wt% hydrogen. The two hydrogen storage materials decompose at a faster rate than either individually and products formed are a mixture of molecular trimers. Digestion of the product mixture formed from the decomposition of the AB + B fuel blend with methanol leads to the two corresponding methanol adducts of the starting material and not a complex mixture of adducts. The work shows the utility of using blends of materials to reduce volatile impurities and preserve liquid phase.

Releasing Hydrogen at High Pressures from Liquid Carriers: Aspects for the H2Delivery to Fueling Stations

“…CBN compounds, i.e., boron-nitrogen containing cyclohexanes, are low melting solids, isoelectronic with BN-methylcyclopentanes, and can release ca. 6 wt % hydrogen in an exothermic reaction in the presence of, e.g., a platinum-nickel catalyst. , Brooks et al . investigated the potential of coupling the exothermic release of hydrogen from the BN group with the endothermic release of hydrogen from the carbon backbone and proposed these materials have the potential to release 12 wt % hydrogen with higher efficiency than the corresponding hydrocarbon compounds (Figure ).…”

“…6 wt % hydrogen in an exothermic reaction in the presence of, e.g., a platinumnickel catalyst. 27,28 Brooks et al 20 investigated the potential of coupling the exothermic release of hydrogen from the BN group with the endothermic release of hydrogen from the carbon backbone and proposed these materials have the potential to release 12 wt % hydrogen with higher efficiency than the corresponding hydrocarbon compounds (Figure 3). Hydrolysis of hydrogen carriers, e.g., sodium borohydride (SBH, NaBH 4 ; Δ r G°= −75 kJ/mol•H 2 ; eq 1) and sodium octahydroborate (OHB, NaB 3 H 8 ; Δ r G°= −75 kJ/mol•H 2 ; eq 2) and ammonia borane (Δ r G°= −45 kJ/mol•H 2 ; eq 3), 29 provides an alternate method to transport hydrogen.…”

Kinetics of −CH2CH2– Hydrogen Release from a BN-cyclohexene Derivative

“…In a similar vein, our group has investigated the consequences of incorporating NH 2 BH 2 units into cycloalkyl structures to form saturated carbon–boron–nitrogen (CBN) heterocycles (Figure ). Our past studies of these mixed organic–inorganic hydrogen storage materials have focused primarily on characterizing H 2 release from the amine–borane groups − , and the overall thermodynamics of the six-membered CBN compounds. , …”