Synthesis and comparative photocatalytic activity of CuO layers on SiO2 substrates

Abstract

Using the thermodynamic and kinetic approaches, it was found that Cu(NH 3) 2+ 4 aq complex predominating at 23 • C spontaneously decomposes at elevated temperatures, forming CuO precipitate in a bulk solution and a layer (CuO||SiO 2) 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(NH 3) 2+ 4 aq 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||SiO 2 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||SiO 2 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.

Colloidal-chemical mechanism of Zn(OH)2-ZnO layer formation at the glass - ammonia solution - Zn(II) interface

“…Elemental analysis by inductively coupled plasma mass spectrometry (Elan 9000, [24]) was used to experimentally determine the kinetics of Zn(II) mass transfer during the transformation of a homogeneous zinc ammine solution into a colloidal Zn(OH) 2 /ZnO solution in the aqueous phase and on the solution-glass substrate interface. The zinc salt solution for the kinetic experiment was prepared by dissolving 4.39 g of chemically pure zinc acetate Zn(CH 3 COO) 2 • 2H 2 O in 60 -70 ml of deionized water (Millipore Simplicity system, solution resistance 18 MΩ•cm).…”

“…The content of zinc, which formed a film on the walls of the quartz glass reactor, was determined after dissolving a layer with 2 mol/l hydrochloric acid with a volume equal to the volume of the studied solution, 5 ml. Along with chemical elemental analysis of Zn(OH) 2 /ZnO formation in (1), layer formation was studied by Dynamic Light Scattering (DLS) and Laser Doppler Electrophoresis measurements carried out on a Zetasizer Nano ZS particle analyzer (Malvern Panalytical Ltd.) [24,25].…”