Preparation, Characterization And Electrochemical Hydrogen Storage Property Of Graphene

Hydrogen is the most promising of the so-called "clean" fuels and the ideal candidate as an energy carrier, due to its high efficiency and nonpolluting nature. Finding a safe, cheap and simple method to store hydrogen is clearly one of the key challenges at present. The storage of electrochemically generated hydrogen under an ambient temperature and pressure has found a wide application in the host materials. Since it was found in2004, graphene, as the fundamental two-dimensional carbon structure with exceptionally high crystal and electronic quality, had attracted increasing interest for the promising potential applications. Besides, its low density, huge specific surface area, high chemical stability, it has been considered as a very promising material for hydrogen storage.In this work, three kinds of graphene sheets have been achieved by the direct current (DC) arc-discharge under hydrogen atmosphere (0.03MPa,0.05MPa and0.07MPa), using pure graphite as the electrodes. And all the samples were characterized by XRD, TEM, Raman, FT-IR and so on. The structure analysis shows that the graphene sheets have few layers (nearly10), wide interlay spacing and rich-wrinkled morphology. The influence of hydrogen pressures (e.g.0.03MPa,0.05MPa,0.07MPa) on the products were investigated.The electrochemical hydrogen storage was investigated to these three kinds of graphene sheets obtained in different hydrogen atmosphere, and their capacity of electrochemical hydrogen storage were7.5mAh/g,107.6mAh/g,147.8mAh/g, respectively. They exhibit a good electrochemical stability with a capacitance gradation of50%over50cycles. Mechanism for electrochemical hydrogen insertion/desertion of such graphene sheet was discussed with respect to the single-layer graphene and multi-layer graphite.Considering that some amorphous phases and carbonaceous particles exist in graphene samples, we designed the thermal treatment process to purify them. And choose two samples (graphene sheets obtained in0.03MPa,0.07MPa H2) to investigate. The samples after purified were characterized by XRD, SEM. The results show that the purified samples get a better quality. Then, the electrochemical hydrogen storage was investigated to these purified samples, their capacity of electrochemical hydrogen storage were87.6mAh/g,242.9mAh/g, respectively. Compared to raw graphene electrodes, their capacity have been improved greatly. And they exhibited a better electrochemical stability with a capacitance gradation of70%over50cycles.