Microwave-hydrothermal synthesis of beta-bismuth (III) oxide nanopowders and their enhanced photocatalytic properties

Facile microwave-hydrothermal method was successfully used to synthesize Beta-bismuth (III) oxide (beta-Bi2O3) nanopowders under the low calcination temperature (350 degrees C) with a demonstrated diameter of about 40-200 nm. UV-vis diffuse reflection spectroscopy revealed that the resulting beta-Bi2O3 nanopowders exhibited a broad absorption with a low band gap of about 2.64-2.85 eV. When the reaction temperature of microwave-hydrothermal process was 180 degrees C (the sample is named as 180 MH), an optimal methyl orange(MO) degradation efficiency of 95.0% was achieved after visible light irradiation of 120 min. beta-Bi2O3 nanopowders also had a strong degradation effect on the tetracycline (TC). Kinetic studies indicated that the photocatalytic degradation process of MO and TC could be well fitted to the pseudo-first-order kinetics. The mechanisms for the enhanced photocatalytic degradation were disclosed as well, and the h(+) and O-2(center dot-) were dominating radicals for MO degradation. This paper provides a way to synthesize nanostructural materials for wide applications. (C) 2020 Published by Elsevier B.V.