Features of Hydrothermal Growth of Hierarchical Co 3 O 4 Coatings on Al 2 O 3 Substrates
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HESIS AND PROPERTIES OF INORGANIC COMPOUNDS
Features of Hydrothermal Growth of Hierarchical Co3O4 Coatings on Al2O3 Substrates T. L. Simonenkoa, b, *, V. A. Bocharovaa, c, Ph. Yu. Gorobtsova, N. P. Simonenkoa, E. P. Simonenkoa, V. G. Sevastyanova, and N. T. Kuznetsova aKurnakov
Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow, 119991 Russia Grebenshchikov Institute of Silicate Chemistry, Russian Academy of Sciences, St. Petersburg, 199034 Russia c Mendeleev University of Chemical Technology of Russia, Moscow, 125047 Russia *e-mail: [email protected]
b
Received April 10, 2020; revised April 27, 2020; accepted April 30, 2020
Abstract—The formation of a hierarchical cobalt(II, III) oxide coating on the surface of a polycrystalline Al2O3 substrate under hydrothermal conditions was studied. Features of the microstructure of the obtained coatings were investigated by scanning electron microscopy; these coatings were shown to consist of Co3O4 nanosheets arranged perpendicular to the surface of the substrate with a blossoming flower-like structure. The production of the coating of the desired composition without crystalline impurities was confirmed by IR spectroscopy, X-ray powder diffraction analysis, and energy dispersive spectroscopy elemental analysis. The roughness of the formed Co3O4 film was estimated by atomic force microscopy. The local electrophysical characteristics of the produced oxide coating (work function of film surface, capacitance, and surface distribution maps of surface potential and capacitance contrast) were studied by scanning capacitance microscopy and Kelvin probe force microscopy. A local analysis of the current–voltage characteristics of the studied samples was made. Keywords: hydrothermal synthesis, hierarchical structures, nanosheets, film, cobalt oxide, Co3O4, supercapacitor DOI: 10.1134/S0036023620090181
INTRODUCTION According to many experts, one of the global challenges of humanity in the XXI century is the exponential increase in the global energy consumption [1, 2]. Solving this challenge requires the development of the energy industry in two directions: the design of modern high-performance energy-generating systems [3– 5] and the creation of reliable energy storage devices [6–8]. In the context of the creation of the latter, of particular importance are supercapacitors, the potential of using which begins with the simplest portable electronics and extends to many industries, including the transport, healthcare, construction, and defense ones [9, 10]. The special operating characteristics of supercapacitors (high specific power, high charge– discharge rate, long service life, environmental safety, and low maintenance cost) enable them to fill the gap in energy efficiency between electrical capacitors and lithium-ion batteries [11, 12]. Among a wide diversity of electrode materials, transition metal oxides are still considered the most promising for creating high-performance supercapacitors because they exhibit several oxidation states and can
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