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Title: Coupling of Exothermic and Endothermic Hydrogen Storage Materials

Chemical hydrogen storage (CHS) materials are a high-storage-density alternative to the gaseous compressed hydrogen currently used to provide hydrogen for fuel cell vehicles. One of the challenges of CHS materials is addressing the thermodynamic and kinetic barriers required to break the chemical bonds and release the hydrogen. Coupling CHS reactions that are endothermic and exothermic during the dehydrogenation can improve the system on-board energy efficiency and thermal control, making such materials viable. Acceptable coupling between reactions requires both thermodynamic and kinetics considerations. Models were developed to predict the reaction enthalpy and rate required to achieve high conversions for both reactions based on experimental measurements. These modeling results show that the efficiency of coupling of an exothermic and endothermic reaction is more sensitive the magnitude of the ratio of the exothermic and endothermic enthalpies than the ratio of the rates of the two steps. The modeling shows further that a slower rate of the endothermic step is desirable to permit sufficient heating of the reactor by the exothermic step. We look at two examples of a sequential and parallel reaction scheme and provide some of the first insight into the required temperature range to maximize the H2 release from 1,2-BN cyclohexanemore » and indoline.« less
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Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Power Sources, 324:170-178
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
Sponsoring Org:
Country of Publication:
United States
Exothermic; Endothermic; Hydrogen Storage; Materials; Hydrogen; Storage; Coupling