Room-temperature nonaqueous synthetic routes turn out to be particularly competitive among all the available liquid-phase synthetic methods for nanometer-sized metal oxides for multiple applications. Microplasma-assisted anodization is employed to prepare soluble and crystalline Mo species in a water-deficient and extraneous ionic-salt-free ethanol electrolyte. The anodization of Mo in absolute ethanol is found to produce Mo oxyethoxide in the liquid ethanol phase, along with a small montage of mixed hexagonal and orthorhombic MoO 3 crystals. The evolution of Mo species in solid and liquid phases is characterized to study the crystallization of MoO 3 crystal and the formation of blue spherical Mo polyoxometalates (POMs) after extended aging. The addition of water in the suspension delayed the formation of molybdenum blue while hydrogen peroxide induced the precipitation of a dendritic framework of hexagonal MoO 3. A thin MoO 3 film was produced from the solution and can be used for humidity sensing by the facile conductivity measurement.
Bibliographical noteFunding Information:
We would like to thank the support from National Natural Science Foundation of China (NSFC) (Nos. 51702264 and 41371275), Fundamental Research Funds for the Central Universities (No. XDJK2017B033), and Research Funding of Southwest University (No. SWU117019). The funding from the Engineering and Physical Sciences Research Council (EPSRC) (under Grant Nos. EP/K022237/1, EP/K036769/1, and EP/M024938/1) is also acknowledged. We also appreciate the funding from the EU COST Action (No. TD1208) for useful exchanges and discussions. We also thank Ms. Zhang Ziye (Southwest University) for the measurement of conductivity under different relative humidity values.
© 2019 American Chemical Society.
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