Hydrogen storage in carbon nanostructures

The connection between the structure of the materials, determined by different characterization methods and the hydrogen storage capacity, will be used as guideline in attempts to produce suitable hydrogen storage materials. The results of the hydrogen storage experiments do not confirm the high hydrogen storage capacities. The highest storage capacities measured at room temperature were 0.4 mass%, which is very far from the highest values of 7-60 mass% reported. It was possible to store 1.3 mass% hydrogen at atmospheric pressure by cooling down to liquid nitrogen temperature. Thus, all the capacities are far from 6.5 mass%, which is a realistic lower limit if a material is to be used for hydrogen storage. The results obtained are in good agreement with some of the results that are being published by other groups around the world, who are also working on the same problem. Hence, accumulating evidence suggests that the high hydrogen storage capacities reported are due to experimental errors. The attempts to produce suitable carbon nanomaterials for hydrogen storage have mostly concentrated on finding ways to produce single-walled carbon nanotubes with a high yield. If the nanotubes are to be used for hydrogen storage the cost should be orders of magnitude less than the current price of 500 US dollar/g. The experiments show that it is possible to produce the nanotubes with good selectivity by decomposing carbon-containing gases on solid catalysts containing Fe and Co. However, without further improvement the production method cannot bring the price down to an acceptable level since the yield of nanotubes is too small. Thus, the conclusion of the project is that no results are obtained that indicate that hydrogen storage in carbon nanostructures will be able to compete with other well-known methods for storing hydrogen