Functionalised Hybrid Poly(ether ether ketone) containing MnO2: investigation of operative conditions for hydrogen sorption

Composite material synthesis, based on Manganese oxide (MnO2) anchored to a functionalized polymeric matrix, was optimized. For this investigation two different MnO2 loadings were selected (16 and 80wt%) in order to understand the relation between the oxide content, chemical-physical characteristic and the H2 sorption properties. SEM, XRD were carried out and the obtained results were correlated to the H2 sorption/desorption characterizations by Sievert apparatus. From these measurements at 50°C/40bar, the sample containing 16wt% of metal oxide content has revealed a low H2 sorption capability (0,04 wt%) instead of the 80wt% sample that showed a very high H2 storage value (3 wt%). A short sorption/desorption cycles were carried out and a good reversibility was revealed. A modelling study, ab-initio Density Functional Theory (DFT) calculations, was carried out. The starting unit cell was MnO2 while Mn24O48 was considered as a supercell. The number of H atoms was gradually increased and desorption energy was calculated. Desorption energy starts from 366 kJ/mol and decreases by increasing the number of H atoms. For the experimental H2 sorption value (1,7wt%) it was calculated the number of the respective H atoms (36) and the corresponding desorption energy (150kJ/mol).