Improvement of hydrogen uptake in iron and vanadium matrices by doping with 3d atomic impurities

cited By 5; The insertion of hydrogen in V and Fe has been investigated by means of pseudopotential DFT calculations with localized basis sets. In Fe and V matrices we have replaced the central atom by a transition metal impurity X = Sc, Ti, Cr, Mn, Fe, Co and Ni to study the capacity of the environment to trap hydrogen. The dissolution energy and structural rearrangement upon H uptake at the different sites close to the doping impurity are calculated. Optimal electronic environments for H trapping are also determined through the calculation of the Fukui function. In the V matrix, the insertion of hydrogen is promoted by doping with the two impurities located at the left of V in the Periodical Table, that is, Ti and Sc. In the iron matrix, among the elements at its left in the Periodic Table, only Mn improves the H uptake, whereas doping with V and Ti worsen the capability of absorbing hydrogen. Finally, the H-H interaction is found to be strongly dependent upon the metal-hydrogen interaction. Elements like Mn or Fe which shorten the H-X distance, exhibit a strong 3d TM state-1s hydrogen state hybridization that seems to wash out the repulsive H-H Coulomb interaction below the 2.0 limit. Addition of a small percentage of Fe or Mn in binary bcc alloys (V-Ti) is suggested to locally enhance the H storage capacity. © 2012 Elsevier B.V. All rights reserved.