Preparation And Hydrogen Storage Of Metal Oxide Doped Graphene Nanocomposites

Hydrogen is the most promising clean energy due to its high efficiency andnonpolluting nature. It has become the inevitable trend of the development in newenergy field, while hydrogen storage is the key of the whole hydrogen energyutilization. In recent years, graphene has attracted many researchers all over the worldbecause of its large surfaces area and unique properties. People research graphene andits composite materials from different angles.In this paper, graphene was prepared by the method of reductive graphite oxide,and then doped metal oxide to graphene surface. The structure analysis of grapheneand its nanocomposites were performed at the mean while. And then we studied theelectrochemical properties of different metal oxide doped graphene by using CV, EISand charge-discharge testing method.1. Graphite oxide （GO） was synthesized from graphite powder by the method ofpre-oxidation. Then graphene prepared by ultrasonic and chemical reduction GO.The component and microstructure of sample was analyzed through FT-IR, Raman,SEM and TEM characterization. Use thermogravimetric analyse the thermal stabilityof the sample. The electrochemical hydrogen storage capacity of graphene is17.64mAh/g, measured by constant current charge and discharge test, it is equal to0.07wt%of the gravimetric uptake.2. Fe₂O₃/GS nanocomposite prepared by the method of coprecipitation. Thecomponent and microstructure of the nanocomposite was analyzed by XRD, Raman,SEM and TEM characterization. The results show that the Fe₂O₃nanoparticlesloaded on the surface of graphene successfully. The shape of the cyclic voltammetrycurves of the composite is close to a rectangle. The charge-discharge test showedthat the hydrogen storage capacity of composite materials is much higher thangraphene.3. We prepared ZnO/GS nanocomposite to discuss the effect of differenttransition metal oxide for the hydrogen storage properties of graphene. The structureanalysis shows the size of ZnO nano particle is greater than Fe₂O₃particle. Thenature of the material is determined by its structure. The CV curve shape is graduallydistorted from rectangular with an increment of sweep rate because of the internal resistance of the composite electrode. The galvanostatic charge-discharge shows thecycle stability of the ZnO/GS is not better, the discharge performance is good, but stillbelow the Fe₂O₃/GS nanocomposites.4. Transition metal oxide can improve the hydrogen storage properties ofgraphene to a certain extent, what effect will be about the main group metal oxide? Inorder to discuss the problem, we prepared MgO/GS nanocomposite. The structurecharacterization showed that the surface of graphene has some defects due to thespecial strong alkaline of MgO. Compared with the pure graphene, the hydrogenstorage capacity has improved after doping the MgO, but the effect is not obviousthan transition metal oxide. At the meanwhile, the cycle stability is not ideal, thehydrogen storage capacity will attenuation to pure graphene after repeated charge anddischarge cycle.