Metal grafted high enthalpy porous solids in hydrogen storage

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Hydrogen is the leading alternative fuel for automotive applications because it has the highest energy per unit weight and produces only water as a byproduct.  However, its implementation has been hindered because it is very difficult to store in a small enough space to be practical.  For this reason, solids have been developed which hold large amounts of hydrogen in compact volumes.  The most important feature in designing such a hydrogen storage material is the binding strength between the hydrogen and the substrate.  This feature determines how much energy is required to either hold the hydrogen or release the hydrogen.  Ideally this value would fall in the range where neither heating nor cooling is required because this places excess demands on automobile design.  For the first time materials possessing a high concentration of sites possessing a close to ideal binding strength for room temperature applications have been synthesized.   This was acheived in our labs by using surface-bound organometallic fragments as principle binding sites via a sigma-H2 complex.  The maximum binding enthalpies of 22.15 kJ/mol are more than twice that previously observed, leading to storage values of 22.15% at -196 °C.  The Ti units on the surface bind 2.7 H2 at this temperature and 1.1 H2 at room temperature.  This proposal aims at systematically optimizing and improving these materials, and related carbon-based analogues to the point where commercial applications are feasible.  These materials will also be explored by various physical techniques at Hydro Quebec, Windsor, NREL and NIST in order to more fully understand the binding mechanism of the hydrogen and further improve performance.