Preparation Of ZnO Hollow Spheres And ZnO/C Spheres Nanocomposites And Their Gas Sensing And Electrochemical Properties

Zinc oxide (ZnO) is a typical n-type metal oxide with a wide band gap of 3.37 eV and a large exciton binding energy of 60 meV. It is an important multifunctional semiconductor with numerous applications such as solar cells, nanolasers, photodetectors, light emitting diodes, photocatalyst, gas sensors, and supercapacitors because of its unique optical, electrical, and physico-chemical properties.In this paper, the main research objects are the synthesis of ZnO nanostuctures, as well as their gas sensing properties and electrode electrochemical properties. Simple template process and water bath method with low temperature were used to prepare ZnO hollow spheres and ZnO/C spheres nanocomposites with different ratio, respectively. The gas sensing properties and the electrode electrochemical properties of the as-prepared ZnO nanostructures were measured by a WS-30A gas sensor measurement system and an electrochemical workstation. The main contents and results could be summarized as follows:(1) Preparation and characterization of ZnO hollow spheres and their gas sensing propertiesZnO hollow spheres were prepared successfully via a simple template process under the water bath condition using zinc acetate as precursor and polystyrene spheres as template. The structural, morphological, componentiol and surface state characterizations of the samples were carried out by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. The gas sensing properties of as-prepared ZnO hollow spheres were tested by a WS-30A gas sensor measurement system. The results show that the sensor exhibits the highest gas response to n-butanol, and the gas response largely depend on specific area and the concentration of the adsorbed oxygen ions on sample surface.(2) Synthesis of ZnO/C spheres nanocomposites and their electrochemical propertiesThe ZnO/C spheres nanocomposites with different ratios (nc:nZno=0～2.5) have been directly synthesized at low temperature (60℃) by a water bath method. XRD, TEM, XPS and BET were used to characterize the microstructure, morphology and composition of the final products. The electrochemical properties of ZnO/C spheres nanocomposites with the different ratios as supercapacitor electrode materials were measured in KOH solution by an electrochemical workstation at room temperature. It is shown that the sample with molar ratio of 1:1 has the highest specific capacitance and the specific capacitance is due to morphology and specific area.