Critical findings during the optimisation of hydrogen storage in vapour grown carbon fibres

摘要

The storage of hydrogen in vapour grown carbon fibres samples, according to different well known manufacturing processes, is studied. The main differences between the samples are: the precursor gases composition; the application of an annealing treatment in different atmospheres; charging by absorption in a high pressure hydrogen atmosphere; and finally, chemical and electrochemical treatments. The techniques used for the fibres characterization were: Rutherford backscattering and elastic recoil detection analysis with 2 MeV He~+ ions. The study shows that the absorption of hydrogen in over-pressurized hydrogen atmosphere is more effective, than chemical treatment and charge by electrolytic processes. The formation of hydrogen hosting sites occurs even with the standard fabrication method, without the need of any of the above mentioned treatments. Annealing under different inert gases are of theoretical interest also, since we show evidence of different translational movement restrictions according to the nature of the inert gas. Even more important, we show that in some circumstances, the anode-cathode current used to measure the stored hydrogen in vapour grown carbon fibres, may not constitute a reliable methodology.