Summary
The concept of hydrogen as an energy carrier can be realised only if efficacious storage media for hydrogen (H2) are found and developed unto technical maturity.
In this context, this sub.project aims to optimise the synthesis of carbon nanofibres (CNF) in terms of their reproducibility and selectivity. To this end, approx. 80 different CNF batches were synthesised. The catalysts required for synthesis used were mainly nickel (Ni)/copper (Cu) catalysts with a variable Cu share; in some cases, iron (Fe)/Cu was also used. The catalysts are realised both by conventional wet precipitation as well as through precipitation in nano-reactors ("micelle route"). In order to produce as pure a phase of the final substance as possible, the participants subjected a number of CNF batches to acid treatment with the intention of extracting the metal catalyst. Precise measurement of the H2 charge capacity, the CNF samples best suited for H2 storage were to be selected and further optimised through activation steps.
In addition to nanofibres, other carbons (carbon aerogels, graphite binder electrodes) are also synthesised or modified for use as lithium storage material.
Results:
- The nanofibre characteristics are significantly determined by the catalyst used and the synthesis route (conventional or micelle technology).
- Fe/Cu-catalysed fibres display the highest crystallinity.
- Complete removal of catalyst residue from the fibres is not possible.
- The graphite-based samples possess substantially higher storage capacities than aerogels or nanofibres (340 mAh/g compared with max. 220 mAh/g).
- All CNF samples displayed H2 charge values too low for technical application at < 0.4 weight percent (expected value between 1 and 5 weight percent). Systematic effects caused by the pretreatment or activation were not discernible.
