Abstract: A candidate hydrogen storage material, M, capable of reaction with hydrogen to form a hydride, MHm (m=number of H atoms per formula unit), and to subsequently release hydrogen on demand, is processed electrochemically to enhance its absorption/desorption properties. For example, a magnesium hydride (MgH2) composition, arranged as a positive electrode, is reduced with lithium ions in a direct current electrolytic cell to form nanometer-size particles of magnesium (and lithium hydride). The cell operation may be reversed to oxidize magnesium to nanometer size particles of magnesium hydride. Thereafter, the nanometer-size particles of M/MHm adsorb and desorb hydrogen at higher yields and under more moderate storage processing conditions.