Electrochemical hydrogen storage

Jurewicz K, Frackowiak E, Beguin F. Towards the mechanism of electrochemical hydrogen storage in nanostructured carbon materials. Appl. Phys. A 2003 in press. 

Those rare-earth AB -type hydrides were quickly utilized in rechargeable nickel metal hydride batteries where electrochemical hydrogen charging and discharging take place at ambient temperature. Such electrochemical hydrogen storage is reversible, when the negative hydride electrode (anode) is combined with the positive Ni electrode (cathode) in the battery cell.. 

As a matter of fact, the first hydrides with practical hydrogen storage capacities were realized in rechargeable nickel metal hydride batteries. For more information on electrochemical hydrogen storage in rechargeable batteries a reader can be referred to several recent reviews on this subject [71-73]. 

Because of their diverse structure, one-third of the tubes are expected to possess metallic character and the remaining two-thirds to behave as semiconductors [2, 3]. CNTs represent potential candidates to be used in field emission [4-6] and nanoelectrical devices [6-10], components of electrochemical energy [11, 12] and hydrogen storage systems [13, 14] and as components in composite materials [15-17]. They represent the ultimate carbon fiber, exhibiting exceptional mechanical properties [18-21] by being up to 100 times stronger than steel [22]. 

Cyclic voltammetry is a well-adapted electrochemical technique to elucidate the mechanism and kinetics of reversible hydrogen storage. An example of voltammetry characteristics, using a microporous activated carbon cloth (ACC) from viscose (ACC . S BEX = 1390 m2 g-1) in 3 mol L 1 KOH, is shown in Figure 8.17. The minimum potential is shifted of -100 mV for each cycle, i.e., toward hydrogen evolution. 

Fetcenko M.A, Venkatesan S., Ovshinsky S.R. (1992) Selection of metal hydride alloys for electrochemical applications, Proc. Symp. on Hydrogen Storage Materials, Batteries and Electrochemistry, PV 92-5, 141-167. 

It is known that the electrochemical hydriding/ dehydriding reactions taking place at a hydrogen storage electrode in an alkaline solution may be simply expressed as follows ... 

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