Abstract
•Bi2O3 thin coat based anodes are prepared by electrodeposition and calcination.•Anodes are calcined at different temperatures and characterized by SEM, XRD and TGA.•Anodes have different surface morphology, XRD patterns and electrochemical stability.•Dye RO4 was completely decolorized at the electrochemically more stable anode.•The optimal electrochemical decolorization parameters and kinetics are determined.
Two anodes were prepared by galvanostatic electrodeposition from an acidic Bi(III) solution on a Ti substrate and calcination in air at 350 °C and 600 °C. The surface coat of the anode calcined at 350 °C displayed irregular, predominantly sheet-like and needle-like morphology and it was composed of α-Bi2O3, with minor amounts of rhombohedral Bi and β-Bi2O3, and traces of ω-Bi2O3. The surface coat of the anode calcined at 600 °C predominantly displayed an oval morphology, and it was composed solely of α-Bi2O3. Only this anode was electrochemically stable. TG analysis showed that it was chemically stable in the investigated temperature range from 25 °C to 600 °C, both in oxygen and nitrogen. This anode was used for electrochemical decolorization of a dye, Reactive Orange 4, in the presence of H2O2. The optimal values for the decolorization parameters (applied current density, H2O2 and Na2SO4 concentration and pH), which provided the fastest decolorization, were determined. Decolorization reactions follow pseudo-first order kinetics.