Synthesis and comparative photocatalytic activity of CuO layers on SiO2 substrates

• Published in: Nanosystems : Physics, Chemistry, Mathematics Vol. 11; no. 5; pp. 601 - 607
• Main Authors: Polyakov, E.V., Tzukanov, R.R., Volkov, I.V., Buldakova, L.Yu, Baklanova, I.V., Lipina, O.A., Zhukov, V.P., Kuznetsova, Yu.V., Tutyunnik, A.P., Maximova, M.A.
• Format: Journal Article
• Language: English
• Published: St. Petersburg St. Petersburg National Research University of Information Technologies, Mechanics and Optics 2020
• Subjects: Ammonia; Benzoquinone; Catalytic activity; Copper oxides; Decomposition; Decomposition reactions; High temperature; Hydroquinone; Photocatalysis; Silica glass; Silicon dioxide; Substrates; Thickness
• ISSN: 2220-8054; 2305-7971
• DOI: 10.17586/2220-8054-2020-11-5-601-607

Using the thermodynamic and kinetic approaches, it was found that Cu(NH3)2+4aq complex predominating at 23°C spontaneously decomposes at elevated temperatures, forming CuO precipitate in a bulk solution and a layer (CuO||SiO2) on the surface of silica glass. The rates of these heterogeneous processes are fairly well described by the 1st-order reaction of decay of the Cu(NH3)4+4aq complex. The formation of the CuO precipitate and layer is a two-step kinetic process. The rate of precipitate formation dominates above 65 °C while the rate of the layer formation prevails below this value. The CuO||SiO2 material synthesized below 65° possesses an optical bandgap of (1.25±0.05) eV, which is smaller compared to the crystals of commercial CuO. The CuO||SiO2 material displays a photocatalytic activity in the reaction of UV-decomposition of benzoquinone-hydroquinone. It was discovered that the photocatalytic activity depends on the thickness of the photocatalyst layer.