Patent ID: 8021533

Claim:
A method of forming nanometer-size particles of a hydride forming material, M, or its hydrogen-containing complement, MHm, where m is the number of hydrogen atoms per formula unit and where MHm has an enthalpy of formation, the method comprising: forming a first electrode of an electrolytic cell in which the active electrode material comprises a chemical equivalent excess of either MHm or M in the form of particles that are larger than nanometer-size; forming a second electrode in which the active material is R which is capable of forming a hydride RHr, where r is the number of hydrogen atoms per formula unit, and RHr has a lower enthalpy of formation than MHm; forming a liquid electrolyte in electrochemical connection with the first and second electrodes and containing R +r ions; and where MHm is in excess with respect to M, electrolytically reducing MHm with R +r ions to form nanometer-size particles of M, and RHr, in the first electrode material; or where M is in excess with respect to MHm, electrolytically oxidizing M to form nanometer-size particles of MHm with RHr in the first electrode material; and, thereafter using nanometer-size particles of M and MHm as hydrogen storage materials by sequentially absorbing hydrogen into M particles and releasing hydrogen from MHm particles.