Hydrogen has a great potential to become a wide-scale, carbon free, sustainable energy carrier of the future. However its implementation and final utilization especially in mobile applications is still limited because of several technological and socio-economical barriers, mainly to do with safe, efficient storage of hydrogen with high gravimetric and volumetric storage capacities. Physisorption into nanoporous materials is an attractive option as it benefits from rapid, fully reversible adsorption/desorption and can store significant amounts of hydrogen at more moderate temperature and pressures conditions than conventional liquefaction (20.3 K) or compression (350‒700 bar). Nevertheless, the critical challenge exists to define the experimental methods that allow accurate hydrogen sorption determination and reduce discrepancies in measurements between different laboratories.This thesis presents an investigation of the experimental methodology of hydrogen sorption in porous materials. A set of nanoporous samples and characterisation techniques have been tested rigorously to explore experimental uncertainty and provide universally reproducible procedures. The validity of the standard methods and some new approaches for experimental data collection and analysis are presented. High repeatability of gas sorption isotherms measured gravimetrically and volumetrically at 77 K on reference TE 7 III carbon beads sample has been demonstrated in-house. A study has been conducted between seven laboratories to evaluate the reproducibility of nitrogen/hydrogen isotherms at 77 K according to a defined test protocol. Statistical analysis yields very good agreement between nitrogen and hydrogen sorption results. The Brunauer-Emmett-Teller surface area of 777.8 ± 6.2 m2 g-1 and Dubinin-Radushkevich micropore volume of 0.3766 ± 0.0078 cm3 g-1, have been determined. The excess hydrogen sorption capacities are found to be 1.65 ± 0.04 wt% and 2.33 ± 0.007 wt% for 1 bar and 20 bar hydrogen pressure, respectively. This study concludes that the accuracy of hydrogen sorption measurements have been pushed forward and methodology proposed here could contribute to improvements in certification of future hydrogen sorption methods.
|Date of Award||31 May 2013|
|Supervisor||Tim Mays (Supervisor)|