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Wind Energy Storage
Published in Thomas Corke, Robert Nelson, Wind Energy Design, 2018
The use of metal hydrides offers an excellent alternative to pressurized storage. Metal hydrides, such as MgH2, NaAlH4, LiAlH4, LiH, LaNi5H6, TiFeH2 and palladium hydride, with varying degrees of efficiency, can be used as a storage medium for hydrogen, often reversibly. Some of these are easy‐to‐fuel liquids at ambient temperature and pressure, others are solids that can be turned into pellets. These materials have good energy density by volume, although their energy density by weight is often worse than the leading hydrocarbon fuels.
Green Hydrogen Energy: Storage in Carbon Nanomaterials and Polymers
Published in Neha Kanwar Rawat, Tatiana G. Volova, A. K. Haghi, Applied Biopolymer Technology and Bioplastics, 2021
Brahmananda Chakraborty, Gopal Sanyal
A huge number of chemical storage systems are under study, involving hydrogenation/dehydrogenation reactions, hydrolysis reactions, ammonia, ammonia borane and other boron hydrides, alane or aluminum hydride, etc., [48]. The most promising chemical approach is invariably the electrochemical hydrogen storage, since release of hydrogen may be controlled by applied electricity. For example, metal hydrides, such as LiH, MgH2, NaAlH4, LiAlH4, LaNi5H6, TiFeH2 and palladium hydride, with changeable degrees of efficiency, can be utilized as a storage method for hydrogen, often reversibly [49]. These materials have great energy density, although their specific energy is habitually worse than the foremost hydrocarbon fuels (Figure 9.4(b)) [50]. Nano-metal hydrides have a number of properties that turn them even better contenders for future hydrogen storage systems [51]. At nanoscale, chemical, and structural properties such as sorption site density and particle size demonstrate a significant improvement in sorption kinetics and temperature for hydrogen diffusion or release. However, the downsides of nanoscale materials comprise poor total sorption capacity and heat transfer. Hydrazine is a promising non-metal hydride for ease in handling and storage. Aluminum has been projected as an energy storage method by many researchers [52, 53]. Hydrogen can be obtained from aluminum by reacting it with water. Before that, aluminum must be exposed from its natural oxide layer. That process requires pulverization and chemical reactions with caustic substances. The byproduct, aluminum oxide, can be recycled back into aluminum with the well-known Hall-Héroult process, causing the process theoretically renewable. Graphene is chemically efficient to store hydrogen efficiently. Upon hydrogenation, graphene becomes graphane. It releases stored hydrogen at 450°C [54].
Measurement of Palladium Hydride and Palladium Deuteride Isotherms Between 130 K and 393 K
Published in Fusion Science and Technology, 2020
M. Sharpe, W. T. Shmayda, K. Glance
Palladium hydride and palladium deuteride isotherms have been measured from 130 to 393 K. The data collected for temperatures below 273 K are the first to be reported in the literature. The measured isotherms show that an increasing quantity of palladium hydride is formed with decreasing temperatures with a maximum HM ratio of 0.75. These data are consistent with the literature where the temperatures overlap. The van’t Hoff diagram shows a dramatic deviation from high-temperature behavior for temperatures less than the critical temperatures of 236 K for protium and 211 K for deuterium. Below these critical temperatures, the data indicate that hydrogen and deuterium are more loosely bound, with energies ~2 to 5 kJ/mol. Such states may be due to limiting subsurface absorption or adsorption onto a saturated palladium hydride surface.
High-selectivity palladium catalysts for the partial hydrogenation of alkynes by gas-phase cluster deposition onto oxide powders
Published in Catalysis, Structure & Reactivity, 2018
Peter R. Ellis, Christopher M. Brown, Peter T. Bishop, Dmitrij Ievlev, Jinlong Yin, Kevin Cooke, Richard E. Palmer
One factor that has been found to affect palladium-catalyzed selective alkyne hydrogenation is the formation of palladium hydride and carbide phases. Palladium hydride phases are known to form readily when reduced palladium catalyst nanoparticles are exposed to hydrogen [32] and can hydrogenate alkenes even in the absence of gaseous hydrogen [33]. The presence of subsurface hydrogen has been found to allow hydrogenation and dehydrogenation reactions to occur more readily than systems where subsurface hydrogen is not accessible [34]. The thermal stability of palladium hydride is limited [35] even in the presence of hydrogen, such as in our system, and also is less stable in smaller nanoparticles [35] whereas more surface hydrogen can be formed due to the larger available surface area [36]. Hence, it seems that the presence of bulk palladium hydride is not a major factor at temperatures where good catalytic performance is observed (T > 50°C for all catalysts). Tew et al. observed the formation of a carbide-like phase of palladium on the exposure of reduced catalysts to 1-pentyne [32]. This was a more stable phase than palladium hydride, and re-exposure to hydrogen did not change the palladium carbide structure appreciably. The formation of palladium carbide was found to be independent of palladium particle size [37] and also to be suppressed at H2/1-pentyne ratios above 10. Our H2/1-pentyne ratio is of the order of 60, and so the presence of palladium carbide phases is unlikely. The factors that affect the amount and nature of palladium carbide formation are not completely understood; it is possible that the formation of palladium carbide species is a characteristic of a good selective hydrogenation catalyst.