Hydrogen metal hydrides

Four different methods to store hydrogen are currently available compressed gas, liquid hydrogen, metal hydrides and sorption on different porous materials (carbon materials, zeolites, metal organic frameworks, etc).2-4... 

Keywords Hydrogen, metal hydrides, intermetallic compounds, phase equilibriums, model of non-ideal lattice gas. 

Application of hydride heat machines (the HHM - the hydride heat pump (HHP), a refrigerator, a heat transformer, the compressor, the accumulator of hydrogen) is justified there where there are sources of low-potential energy or a plenty of wasted heat is not used. Systems hydrogen-metal hydrides promote improvement of ecological conditions and introduction of cleaner hydrogen technologies. 

Hydrogen Metal hydrides, in particular lithium hydride... 

A method of chemically synthesizing reduced products including methanol from carbon dioxide and hydrogen has been developed. The method utilizes a metal hydride foil membrane as a continuous source of reactive surface hydrogen atoms and an electrostatic field to enhance the adsorption of carbon dioxide and bicarbonate onto the hydrogen rich surface. The subsequent chemical(rather than electrochemical) reaction between the adsorbed carbon dioxide and surface hydrogen/metal hydride results in the formation of reduced products. 

These Nernstian equations should be modified to indicate the effect of the electric field superimposed on the chemical potential of the surface hydrogen/metal hydride. One possible way to treat this is with the thermodynamic concept of electrochemical potential defined by Guggenheim. The electrochemical potential is defined as ... 

Catalysts are prepared by one of two methods. The support material is impregnated with the metal ion, then heated in air at a high temperature to form the metal oxide. Alternatively, when the support material is an oxide such as alumina, the two oxides are coprecipitated and dried in air. In such case the catalyst is activated by treatment with a reducing agent such as hydrogen, metal hydride, or carbon monoxide. The function of the support appears to be more than simply providing a large surface area. Some type of interaction must occur between the metal oxide and support because the oxide alone behaves differently. 

FIGURE 23.11 Hydrogen metal hydrides characterized in alog (pressure/atm) vs. 1000/(temperature/K) plot. 

Wang, X.L. and Suda, S., Reaction-kinetics of hydrogen metal hydride systems, International Journal of Hydrogen Energy, 1990, 15(8) p. 569-577. 

Metal hydride is an intermetallic compound that traps hydrogen at moderate pressures. It stores large amounts of hydrogen in an exothermal diffusional process. Some drawbacks are its cost and its heavy weight, and its requirement for very pure hydrogen. Metal hydride advantages include convenience, compactness, stable storage, and intrinsic safety. 

The four general approaches for on-board vehicle applications (compressed hydrogen gas, liqnefied hydrogen, metal hydrides, and carbon sorbents) have been discnssed in detail elsewhere and will not be repeated here (Department of Energy, 1999 Hynek et al., 1997 Schlapbach and Ziittel, 2001). 

Marinescu-Pasoi L et al (1991) Hydrogen metal hydride storage with integrated catalytic recombiner for mobile application. Int J Hydr Energy 16(6) 407 12... 

Although a preferred fuel for military applications would be logistic fuel (JP-8), because of difficulties in reforming this fuel, particularly on such a small size, the same fuels used for nonmilitary applications, such as hydrogen, metal hydrides, chemical hydrides methanol, are acceptable as long as they are supplied in closed canisters or cartridges and do not have to be dispensed. 

Hydrogen can be stored as a compressed gas or liquid, or in reversible or alkali metal and chemical hydrides. The advantages of storing hydrogen as a compressed gas are simplicity, indefinite storage time and no purity limits on the hydrogen. Metal hydride compounds must have the following characteristics ... 

---