Production of H₂ from Combined Endothermic and Exothermic Hydrogen Carriers

Abstract

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.

Complex and liquid hydrides for energy storage

“…Another advanced strategy is to use the heat generated in an exothermic reaction to drive a second endothermic reaction [107], an approach also employed in the autothermal reforming of hydrocarbons [108]. Wechsler et al proposed a mixture of an exothermic and endothermic hydrogen storage material to make a single thermoneutral reaction.…”

Enhanced Fuel Cell Performance of Decalin Treated Nafion® Membranes

“…However, the practical energy density of a hydrogen-based fuel cell system is limited by the absence of safe and economical methods of hydrogen storage and distribution. Recent advances in the reversible dehydrogenation/hydrogenation of carbocyclic and heterocyclic hydrocarbons [6][7][8][9][10] motivated our group to re-evaluate such materials as potential direct and regenerable fuels [11]. The use of organic fuels as virtual hydrogen carriers could provide an attractive alternative to hydrogen gas.…”

“…Fuel cells utilizing hydrocarbons have been evaluated as early as the 1960s [2], however high anode overpotentials contributed to low power densities limiting further development [3][4][5]. Recent advances in the reversible dehydrogenation/hydrogenation of carbocyclic and heterocyclic hydrocarbons [6][7][8][9][10] motivated our group to re-evaluate such materials as potential direct and regenerable fuels [11]. Of particular interest is the electrochemical dehydrogenation of cyclic hydrocarbons to stable organic molecules, protons and electrons without production of hydrogen and carbon dioxide.…”

Single-catalyst high-weight% hydrogen storage in an N-heterocycle synthesized from lignin hydrogenolysis products and ammonia

“…Consequently, large-scale automated and especially decentralized energy applications for domestic or commercial buildings seem feasible by means of NEC and an appropriate catalyst2324. The hydrogenation of NEC can be accomplished by heterogeneous ruthenium (Ru) catalysts1025 while palladium (Pd)-based solid catalysts have been reported to be efficient in the dehydrogenation of NEC26. Reusable single catalysts would extend the applicability of NEC-based hydrogen storage significantly.…”