A review on kinetic models and corresponding analysis methods for hydrogen storage materials

The metallic vanadium has an excellent hydrogen storage properties in comparison to other hydride forming metals such as titanium, uranium, and zirconium. The gravimetric storage capacity of vanadium is over 4 wt% which is even better than AB2 and AB5 alloys. The metallic vanadium has shown high hydrogen solubility and diffusivity at nominal temperature and pressure conditions. Consequently, vanadium is under consideration for the cost-effective hydrogen permeation membrane to replace palladium. The issues with vanadium are poor reversibility and pulverization. The poor reversibility is because of high thermal stability of β (VH/V2H) phase which eventually restricts the cyclic hydrogen storage capacity up to 2 wt% at room temperature. The pulverization is because of large crystal misfit between the metal and metal hydride phase. The hydrogen solubility, phase stability, hydrogenation-dehydrogenation kinetics, and pulverization are highly influenced by the presence of an alloying element. Therefore, worldwide efforts are to explore and optimize the alloying element which could enhance the hydrogen solubility, destabilized the β phase, improved the hydrogenation-dehydrogenation kinetics, and prevent the pulverization. The current review is a systematic presentation of these efforts to resolve the issues of vanadium as a base material for hydrogen storage and permeation membrane.

Development of vanadium based hydrogen storage material: A review

Subnitrides strongly enhance the efficiency of Ta3 N5 -nanotube photoanodes in photochemical water splitting. The fabrication of Ta3 N5 nanotube layers with a controlled subnitride layer at the interface to the back contact is demonstrated. The insertion of this subnitride layer has a strong influence on the electron transfer to the back contact, and as a result leads to a drastic shift in photocurrent onset potential and a considerable enhancement of photocurrent conversion efficiency.

Strongly Enhanced Water Splitting Performance of Ta3 N5 Nanotube Photoanodes with Subnitrides.

Surface modification of MgH2 by ZrCl4 to tailor the reversible hydrogen storage performance

High performance FeTi – 3.1 mass % V alloy for on board hydrogen storage solution

Hydrogen absorption kinetics of V4Cr4Ti alloy prepared by aluminothermy

Hydrogen solubility was studied in vanadium and series of vanadium aluminum alloys at varying temperatures and pressures. The alloys were prepared through aluminothermy followed by electron beam refining and consolidation through vacuum arc melting. The consolidated buttons were hot rolled into 1.2 mm strips. The strips were cut into small pieces. The specimens so obtained were annealed to release the stresses developed during hot-rolling. Hydrogen gas was charged in the specimens at present temperatures and pressures. It was observed that hydrogen solubility decreases linearly with aluminum contents. The decrease in the hydrogen solubility with the aluminum content has been explained on the basis of increase in the Fermi energy level arising from the contribution of electrons by the solute aluminum atom to the valence band of the host matrix vanadium.

Terminal solid solubility of hydrogen in V–Al solid solution

Effect of nickel addition on the solubility of hydrogen in tantalum

V4Cr4Ti alloy is synthesized by aluminothermy process followed by electron beam refining. Hydrogen absorption characteristics of the alloy have been evaluated by measuring the pressure composition isotherm (PCIT) at 57 °C temperature. Two plateau pressures are observed in the PCIT curve. Substantial decrease in the hydrogen absorption capacity of the alloy as compared to vanadium has been recorded. Hydrogen absorption kinetics of the alloy was investigated in the temperature range of 200–500 °C. Three-dimensional diffusion appears to be the rate controlling step of the hydrogen absorption. The apparent activation energy was calculated as 0.16 eV/atom-hydrogen.

SYNTHESIS AND HYDROGEN ABSORPTION KINETICS OF V4Cr4Ti ALLOY

The volume expansion of tantalum due to the dissolved hydrogen has been determined using Bragg equation. The hydrogen was dissolved in the pure tantalum metal at constant temperature (360 °C) and constant pressure (132 mbar) by varying the duration of hydrogen charging. The amount of dissolved hydrogen was within the solid solubility limit. The samples with different hydrogen concentration were analyzed by X-ray diffraction technique. Slight peak shifts as well as peak broadening were observed. The relative changes of lattice parameters plotted against the hydrogen concentration revealed that the lattice parameters varied linearly with the hydrogen concentration.

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Manju Taxak

Papers

Hydrogen absorption kinetics of V4Cr4Ti alloy prepared by aluminothermy

Terminal solid solubility of hydrogen in V–Al solid solution

Effect of nickel addition on the solubility of hydrogen in tantalum

SYNTHESIS AND HYDROGEN ABSORPTION KINETICS OF V4Cr4Ti ALLOY

Change in lattice parameter of tantalum due to dissolved hydrogen