The Hydrothermal Synthesis Of Nano-MoO₃and Study On Its Gas Sensing Properties

As a wide-band n-type semiconductor with the special layered structure, MoO3iswidely used in electrical, catalytic and gas sensing fields. MoO3is a kind of famousfunction materials, which attracts more and more researchers in recent years. In general,the research on synthesis and properties of MoO3is less than some other metallic oxides,such as ZnO, TiO2and SnO2.That may be because the price of molybdenum is higher.So, it makes sense to explore the synthesis ways and properties of MoO3deeply.Now, there are many ways to prepare MoO3with high purity. But it’s still achallenge to find a more simple, efficient, and lower cost way to prepare MoO3with anano size. At present, nanotechnology is a hot research area all over the world, which isbecause the size of material has a big influence on its properties. When the grain size isreduced to nano size, the material will show some properties absolutely different fromother ordinary materials. Based on this background, we start our research aimed on theexploration of the synthesis and morphology control ways of MoO3. Besides, we studythe influence of morphologies on MoO3’s gas sensing properties. The main points of thispaper are as follows.At first, we investigated the influence of acids on the product in the hydrothermalreaction. When different kind of acids was added, the products were all orthorhombicone-dimensional MoO3, which was related to the atomic arrangement of MoO3.Then we investigated the effect of additives. The results show that when someadditives were added, no MoO3product can be obtained because of the reactions ofadditives and molybdate. But when some other additives were added, the primarypreferred orientation growth of MoO3crystals was affected, resulted in the changes ofmorphology. In this section, we focused researches on the influence of common cationicsurfactant CTAB and the corresponding forming mechanism was discussed. Because theCTAB micelle keeps different shape under different concentration, this results in thedifferent final morphologies.At last, we tested the gas sensing properties of MoO3samples with somerepresentative morphologies, including nanobelts, nanonets, micron particles and theurchin structures. The sensitivity-temperature curves and dynamic response-recoverytime curves of samples in500ppm ethanol gas were drawed, the results showed that theoptimum working temperature of the samples for ethanol gas were all about250℃. The nanonets samples showed the best sensitivity because of its highest specific area andnumerous porous structure. The urchin-like sample and nanobelts sample showed highersensitivity than the micron particles sample. What’s more, the response and recoverytime for500ppm ethanol gas of the samples are all less than10s at250℃, whichindicates that the molybdenum trioxide is a kind of outstanding gas sensing materials.