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 (β-Bi 2 O 3 ) nanopowders under the low calcination temperature (350 °C) with a demonstrated diameter of about 40–200 nm. UV–vis diffuse reflection spectroscopy revealed that the resulting β-Bi 2 O 3 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 °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. β-Bi 2 O 3 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 •- were dominating radicals for MO degradation. This paper provides a way to synthesize nanostructural materials for wide applications.