Nanomaterials for Hydrogen Storage Application

Hydrogen storage cuts across both hydrogen production and hydrogen applications and thus assumes a critical role in initiating a hydrogen economy. Nanostructured materials have potential promise in hydrogen storage due to their unique features such as adsorption on the surface, inter- and intra-chain boundaries, and bulk absorption. Additionally, they also lead to the design of lightweight hydrogen storage systems with better hydrogen storage characteristics. In this contest, ITAE research group is studying different kinds of materials, having interesting H2 sorption capability in not drastic conditions of temperature and pressure. Among all, composite polymer and natural materials characteristics in terms of morphology, crystallographic structure and H2 sorption capability are studied. The materials based on polymeric matrices have been widely investigated since they ensure an easy handling, good stability in air atmosphere, low cost and weight. In this work, the development of a manganese oxide (MnO2) supported on polymeric matrix based on a functionalized Poly-ether-ether-ketone (PEEK) was optimized starting from a previous study [1]. The MnO2 content depends on synthesis parameters such as concentration of the metal oxide precursor, time and temperature of reaction. Increasing the reaction temperature by 50 to 80-95°C the aggregates size change from 300nm to 28nm modifying the H2 sorption capability also (from about 3wt% to 1wt%). Increasing the MnO2 percentage decreases the polymer support, as evidenced by XRD profiles. After different tests, a standardised synthesis procedure was established and reversibility performances at 50°C/40bar was recorded. Other class of materials here reported is of natural source. Two different volcanic samples, coming from two different eruptions (1892), first sample and second (2006), were analysed, in order to understand the composition and the purity influence on H2 storage capability. First sample, as highlighted by XRD and XRF characterisations, shows oxidized metals, due to a long exposition to the atmospheric agents. On the contrary, second sample obtained during a 2006 summit on the volcano, was not contaminated. An activation procedure for both materials, after different H2 sorption tests and calcination phase, was established. An increase of particle size after calcination step, from about 100nm to 200nm, for first sample was revealed instead of second one where its value remain quite constant. Interesting H2 sorption values are obtained following step-by-step procedures at 30°C/40bar: first sample 3wt% after over than 400hrs, second sample 4wt% after about 300hrs. A reduction of H2 sorption kinetic was revealed, for first sample, following a single step at 40bar (from about 400hrs to 300hrs).