Tailoring the hydrogen desorption thermodynamics of V2H by alloying additives

Vanadium could be a potential candidate for on board hydrogen storage application because of its high gravimetric hydrogen storage capacity (∼3.8 mass%) which is even better then the most widely explored AB5, AB2 & AB intermetallic compounds. Hydrogen absorption of vanadium takes place at ambient temperature and pressure with fast kinetics. The vanadium hydride (VH2) releases hydrogen in two steps: (1) VH2(γ)(s) ↔ ½ V2H(β)(s) and (2) V2H(β)(s) ↔ 2V(s) + ½ H2(g). First step is achievable at the ambient temperature and pressure conditions while, the second step requires high temperature (590 K). Thus only half of the total hydrogen storage capacity is available for use on subsequent absorption-desorption cycles at the ambient temperature. The usable hydrogen storage capacity of VH2 at ambient conditions could be enhanced by tailoring the thermodynamics and kinetics of second step of hydrogen desorption reaction. This could be possible by selecting suitable alloy additives. The present study deals with the selection criteria of alloy additives based on the electronic consideration to tailor the hydrogen desorption thermodynamics and kinetics of V2H.