Influence of the Nb2O5 distribution on the electrochemical hydrogenation of nanocrystalline magnesium

Nanocrystalline Mg powder without and with 2 mol% Nb2O5 catalyst was studied as an electrode material for electrochemical hydrogen charging in a 6M KOH electrolyte. A strong influence of the compaction parameters, the current density and the catalyst on the hydrogenation behavior was observed. The addition of graphite and PTFE to the Mg/Nb2O5 electrodes improves the charging kinetics as well as the hydrogen content. The hydrogen contents achieved in Mg with Nb2O5 however, show a broad scatter. It was concluded that the catalyst distribution influences the upper limit of the storage capacity as well as the oxidation process at the surface during preparation. Since the addition of Nb2O5 was observed to reduce the hydrogen overpotential of Mg depending on the catalyst distribution, it is assumed that the catalyst influences the electrode reactions. Therefore, hydrogenation was investigated for different Nb2O5 distributions at different current densities in detail. (C) 2006 Elsevier B.V. All rights reserved.