The Electrochemical Hydrogen Storage Property Of Different Carbon Nanomaterials

Hydrogen is regarded as the energy of the future. Hydrogen storage is the key process of the hydrogen utilizing system. Conventional hydrogen storage methods include high pressure gas cylinders, liquid hydrogen and metal hydrides, but all of which can't meet the need of vehicle cell. Carbon nanomaterials may be the most promising candidates for hydrogen storage because of its special structure and properties, so the research of the hydrogen electrochemical storage has been the focus of the world.In this work, we centered on the electrochemical hydrogen storage properties of different carbon nanomaterials, including carbon nanotubes, ordered mesoporous carbons and carbon aerogels.The MWNTs were pretreated with acid treatment and carbonization. The morphologies, structures of the MWNTs before and after pretreatment were investigated by TEM and IR. Their electrochemical hydrogen storage capacities were tested by Galvanostatic charge-discharge measurement. The results showed that acid treatment had promoted the hydrogen storage capacity of MWNTs and the hydrogen storage capacity of MWNTs descended greatly after carbonization.Ordered mesoporous carbon materials were successfully synthesized by an easy method of the carbonization of sulfuric-acid-treated silica/triblock polymer/sucrose composites. The morphologies, structures and pore characteristics of the carbon materials were investigated by X-ray diffraction (XRD), nitrogen adsorption-desorption and transmission electron microscopy (TEM and HRTEM) measurements. Their electrochemical hydrogen storage capacities were tested by Galvanostatic charge-discharge measurement. The results showed that the carbon material ( C-P) with higher specific surface area (720m²/g) and pore volume (0.86cm³/g) had higher hydrogen storage capacity (70.1mAh/g) than the carbon material (C-S) with low specific surface area (610m²/g) and pore volume (0.66cm³/g). Both two ordered mesoporous carbons exhibited higher hydrogen storage capacity than the single-walled carbon nanotubes (25.9mAh/g). The Cyclic voltammetry measurement indicated that the ordered mesoporous carbon electrode possessed high electrochemical active than single-walled carbon nanotubes electrode.Spherical carbon aerogels were prepared through the sol-gel polymerization of formaldehyde with the potassium salt of 2,4-dihydroxybenzoic acid using an inverse emulsion polymerization, under the catalyst of potassium carbonate. Spherical carbon aerogels were characterized by SEM,N₂ adsorption. On the basis of comparing the surface areas and pore properties of three carbon aerogels obtained by changing the content of the catalyst, their electrochemical hydrogen storage capacities were tested by Galvanostatic charge-discharge measurement. The results showed that the electrochemical hydrogen storage capacity of the spherical carbon aerogels were decided by surface areas and content of micropores.Fe-,Co- and Ni-doped spherical carbon aerogels were prepared through sol-gel polymerization of formaldehyde with the potassium salt of 2,4-dihydroxybenzoic acid, followed by ion exchange with Fe(NO₃)₃,Co(NO₃)₂ and Ni(NO₃)₂. The electrochemical hydrogen storage capacity of the spherical carbon aerogels before and after Fe-,Co- and Ni-doped was tested by Galvanostatic charge-discharge measurement. The results showed that the electrochemical hydrogen storage capacity was greatly enhanced after Fe-,Co- and Ni-doped, while the cycle performance of the electrode was poor.The carbon aerogels and LaNi₅ composites were obtained by adding LaNi₅ powder into the RF sol before aging and carbonizing. The morphologies, structures and pore characteristics of the composites were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The electrochemical hydrogen storage capacity of the composites were tested by Galvanostatic charge-discharge measurement. The results showed that the electrochemical hydrogen storage capacity of the composites were effected by the content of the LaNi₅ hydrides. If there was few LaNi₅ hydrides in the composite, it will lower the electrochemical hydrogen storage capacity of the carbon aerogels electrode while the results will be better if the content of the LaNi₅ hydrides increased.