Hydrogen multicenter bonds and reversible hydrogen storage

摘要

A new strategy for reversible hydrogen storage based on the properties of hydrogen multicenterbonds is proposed. This is demonstrated by carrying out ab initio calculations of hydrogen saturationof titanium and bimetallic titanium-aluminum nanoclusters. Hydrogen saturation leads to theformation of exceptionally and energetically stable hydrogen multicenter bonds. The stabilizationresults from sharing of the hydrogen atom electron density with the frontier orbitals of the metalcluster. The strength of the hydrogen multicenter bonds can be modulated either by varying thedegree of hydrogen loading or by suitable alloying. Mode-specific infrared excitation of thevibrational modes associated with the multicenter hydrogen bonds can release the adsorbedhydrogen, thereby enabling efficient reversible hydrogen storage. The possible formation ofhydrogen multicenter bonds involving titanium atoms and its implication to hydrogen adsorption/desorption kinetics in hydrogen cycled Ti-doped NaAlH_4is also discussed.