Innovative materials for hydrogen storage

One of the main challenges for today’s society is to find alternative energy sources to fossil fuels. Hydrogen is the most suitable candidate because it has a high energy density (33.33 kWh)and its only reaction product is H2O. Due to extremely low density of this gas, solid-state storage system is the most viable solution.[1] As alternative and promising materials for this purpose we are evaluating perovskite oxides because these materials have a high thermal stability, they are relatively active, they allow the exploitation of a great variety of elements in the composition while maintaining the basic structure unchanged and, to improve its efficiency, it is also possible to easily vary the stoichiometry.[2] Specifically, we are considering ABO3±δ type perovskite oxides with a non-stoichiometric content of oxygen to investigate whether the presence of oxygen vacations can promote the amount of hydrogen absorbed. We are also evaluating the addition of small amounts of Pd0, which should promote the dissociation of hydrogen and, therefore, improve the ab/desorption kinetics of this gas. Among the investigated materials, CaMnO3 (CM) is the most promising in terms of hydrogen storage. The H2 absorption and desorption analysis as a function of pressure were carried out with a High Pressure Gas Sorption Analyzer (i-Sorb Anton Paar). Measurements carried out at 40 bar of H2 and at different temperatures have shown that the non-stoichiometric amount of oxygen affects the hydrogen storage capacity. In particular, the structures with an excess of oxygen exhibit a higher H2 absorption capacity. In fact, at 100 °C, CM absorbs 0.44 kg/m3 of H2 and the uptake of H2 for CMO3±δ is 0.98 kg/m3. Moreover we observed that, in the same conditions, these materials in presence of Pd0 absorbs 12.88 kg/m3 and 44.95 kg/m3 of H2 respectively. Ongoing activities are focused on investigating the gas release conditions and on eventual structural modifications. References [1] D. J. Durbin, C. Malardier-Jugroot, International journal of hydrogen energy. Review of hydrogen storage techniques for on board vehicle applications., 2013, 38(34), 14595-14617. [2] Ibrahim, S. M. A. A. Hydrogen storage in proton-conductive perovskite-type oxides and their application. Korean J. Chem. Eng. 2014, 31, 1792-1797.