(25f) Hydrogen Storage Using Mg-Mixed Metal Hydrides

Hydrogen
Storage Using Mg-Mixed Metal Hydrides

To
minimize the adverse effect of ever increasing global energy consumption per
capita, there is a need for significant energy production from renewable
resources and non carbon molecules such as hydrogen to become energy carrier.
The lack of satisfactory hydrogen storage systems which are safe, cheap and
simple is one of the main problems for the transition to a hydrogen-based
energy carrier system. Mg-based alloys show potential as hydrogen storage
material because of the high gravimetric density of MgH₂ (7.6 wt.
%), as well as its abundant supply and low cost as a raw material. However,
they exhibit high enthalpies of formation, poor hydrogenation/dehydrogenation
kinetics, poor charge/discharge cycling stability and high temperature
requirements. Literature studies showed that the addition of LaNi₅
to MgH₂ reduces hydrogen absorption temperature and accelerates the
kinetics at room temperature and yields higher hydrogen storage capacity at
elevated temperatures. Furthermore, literature showed that Nb₂O₅
is the most effective catalyst for the hydrogen sorption reaction of Mg.

In
this work, Mg-LaNi₅ and Mg-Nb₂O₅ composite
systems were prepared and studied to obtain a better understanding of hydrogen
storage capacity, adsorption/desorption rates. Hydrogen storage capacities of
our sorbent were measured by performing adsorption/desorption experiments at
different temperatures.

The
results of the experiments were analyzed and compared with available data from
the literature. The results of our experiments showed that our sorbent (MgH₂
- 20 wt. % LaNi₅ - 7.3 wt. % Nb₂O₅) has
higher capacity for absorption and higher rate of absorption and desorption at
different temperatures than the available sorbents in the literature today.