Synthesis And Gas Sensitive Properties Of Reduced Graphene Oxide And Its Composites

As a new type of two-dimensional crystal material, graphene has drawn greatattention of researchers around the world since it was found in2004. Its unique structureprovides it with excellent physical and chemical properties such as excellent mechanics,thermal properties, high specific surface area, excellent electrical conductivity and so on.Graphene has broad application prospect in gas sensors for these excellent performances.On the one hand, its single layer2-d structure enables nearly all carbon atoms to beexposed to target gas, which is in favor of its sufficient touch with the gas molecules. Onthe other hand, graphene has low Johnson noise. These two characteristics make itpossible for graphene as gas sensitive material to detect relatively lower concentrations ofgases.In this paper, we prepared the reduced graphene oxide(RGO) and the compositematerials of RGO by chemical oxidation reduction method. The XRD, Raman spectra,SEM and TEM characterization methods were utilized to do characterization on themorphology and structure and the gas-sensing properties of the materials were studieddeeply. The concrete contents were as follows:(1) The graphite oxide was prepared by modified Hummers method and grapheneoxide was obtained by ultrasonic processing. The XRD, Raman and TEM were used tocharacterize the structure and morphology of the GO. The results showed that the preparedGO was stripped well with thin lamella.(2) Through a variety of reduction methods (for example, hydrazine hydrate, sodiumborohydride, ascorbic acid, hydrothermal method and thermal reduction), the GO wasreduced and the prepared RGO had different reduction degree. Then thorough research onthe gas-sensing properties of the prepared RGO was conducted. It was shown that in thenormal temperature test, the RGO prepared by hydrothermal method and thermalreduction processing at200degrees had higher sensitivity and under the condition ofheating2.4V, the sample could still maintain higher sensitivity. With the increase of temperature, the sensitivity of graphene materials decreased, but the response andrecovery speed had great improvement.(3) Using500℃thermal treatment of graphene oxide/nickel nitrate mixture, we gotRGO/Ni nanocomposites by one step. By observing the morphology of composite, we sawthat the nickel was dispersed evenly in RGO. The NO2gas sensing test showed that underthe condition of normal temperature, the composites shown better gas sensitiveperformance than pure RGO; Under the heating voltage of2.4V, composite materialscould still maintain good gas-sensing properties, while pure RGO gas sensor had a largerdecline in performance.