Perovskite oxides as efficient solution for solid state hydrogen storage

As it is known, fossil fuel are not inexhaustible and not sustainable energy sources. For these reasons it is necessary to find more sustainable alternatives. Among different candidates, hydrogen, due to its high energy density (120 MJ/kg = 33.33 kWh), seems to be the most suitable solution, also because its only reaction product is H2O.1 As material for solid state hydrogen storage we are investigating CaMnO3, an ABO3 perovskite oxide, whose constituent elements are earth-abundant and nontoxic. These types of materials exhibit 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 Particularly, CaMnO3 was synthesized according to a modified Pechini method and characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) microscopy analyses. Subsequently, to improve the hydrogen sorption by the material, Pd0 was added (1% wt.) because it is argued that it promotes the dissociation of hydrogen molecule into atoms, helping their absorption. According to our results obtained with a volumetric system (i-Sorb, Anton Paar) and 500 mg of material, CaMnO3/Pd 1% has a hydrogen storage capacity equal to 0.86% wt. (equivalent to 38.70 kg/m3) at 40 bar and 100 °C. The scalability and reproducibility of this material were additionally investigated with a larger scale bench apparatus at DLR (Institute of Engineering Thermodynamics, Germany). In the test bench a sample amount of 9 g has been tested and in these conditions, the storage capacity of CaMnO3/Pd 1% was found to be equal to ̴ 0.8 wt%, confirming scalability and good reproducibility for this material. The gas release conditions and eventual structural modifications for the larger scale apparatus are currently under investigation. References [1] M. Kunowsky, J. P. Marco-Lózar, A. Linares-Solano, Journal of Renewable Energy,2013, 2013, 1- 16. [2] S. M. A. A. Ibrahim, Korean J. Chem. Eng. 2014, 31, 1792-1797.