This paper reports the kinetics of hydrogen generation from the reaction between sodium borohydride and methanol, water, and their mixtures over a temperature range between -20 and +50 °C. Hydrogen generation was found to obey a first-order rate law with respect to sodium borohydride concentration for each of the four reacting mixtures of methanol, "nearly dry" methanol (2:1 water to sodium borohydride mole ratio), "wet" methanol (10:1 water to sodium borohydride ratio), and water, with activation energies of 53.0 ( 3.4, 52.3 ( 9.5, 36.1 ( 2.8, and 86.6 ( 8.0 kJ/mol, respectively. Methanolysis of sodium borohydride was shown to be a feasible method for low-temperature hydrogen generation. However, this noncatalytic reaction system exhibited large lag time and slow reaction kinetics at low temperatures. Our study indicates that the reaction system based on sodium borohydride and the nearly dry methanol can be a potential high gravimetric density hydrogen storage system.

Substituted piperidines and octahydroindoles are compared in terms of their usability as reversible organic hydrogen storage liquids for hydrogen-powered fuel cells. Theoretical Gaussian calculations indicate which structural features are likely to lower the enthalpy of dehydrogenation. Experimental results show that attaching electron donating or conjugated substituents to the piperidine ring greatly increases the rate of catalytic dehydrogenation, with the greatest rates being observed with 4-aminopiperidine and piperidine-4-carboxamide. Undesired side reactions were observed with some compounds such as alkyl transfer reactions during the dehydrogenation of 4-dimethylaminopiperidine, C-O and C-N cleavage reactions during hydrogenation and/or subsequent dehydrogenation of 4-alkoxy and 4-amino indoles, and disproportionation during the hydrogenation of 4-aminopyridine.

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One of the major limitations to the use of fuel cell systems in vehicular transportation is the lack of hydrogen storage systems that have the required hydrogen storage density and moderate enthalpy of dehydrogenation. Organic liquid H(2) carriers that release H(2) endothermically are easier to handle with existing infrastructure because they are liquids, but they have low storage densities and their endothermicity consumes energy in the vehicle. On the other hand, inorganic solid H(2) carriers that release H(2) exothermically have greater storage densities but are unpumpable solids. This paper explores combinations of an endothermic carrier and an exothermic carrier, where the exothermic carrier provides some or all of the necessary heat required for dehydrogenation to the endothermic system, and the endothermic carrier serves as a solvent for the exothermic carrier. The two carriers can be either physically mixed or actually bonded to each other. To test the latter strategy, a number of chemically bound N-heterocycle:BH(3) adducts were synthesized and in turn tested for their ability to release H(2) by tandem hydrolysis of the BH(3) moiety and dehydrogenation of the heterocycle. To test the strategy of physically mixing two carriers, the hydrolysis of a variety of amine-boranes (H(3)N:BH(3), Me(2)HN:BH(3), Et(3)N:BH(3)) and the catalytic dehydrogenation of indoline were carried out together.