Novel pure α-, β-, and mixed-phase α/β-Bi2O3 photocatalysts for enhanced organic dye degradation under both visible light and solar irradiation

Abstract

Combining the pure α- and β-phases of bismuth oxide enhances its photocatalytic activity under both visible and solar irradiation. α-Bi2O3, β-Bi2O3, and α/β-Bi2O3 were synthesized by a solvothermal calcination method. The structural, optical, and morphological properties of the as-synthesized catalysts were analyzed using XRD, UV-DRS, XPS, SEM, TEM, and PL. The bandgaps of α/β-Bi2O3, α-Bi2O3, and β-Bi2O3 were calculated to be 2.59, 2.73, and 2.34 eV, respectively. The photocatalytic activities of the catalysts under visible and solar irradiation were examined by the degradation of carcinogenic reactive blue 198 and reactive black 5 dyes. The kinetic plots of the degradation reactions followed pseudo-first-order kinetics. α/β-Bi2O3 exhibited higher photocatalytic activity (∼99%) than α-Bi2O3 and β-Bi2O3 under visible and solar irradiation. The TOC and COD results confirmed the maximum degradation ability of α/β-Bi2O3, and the decolorization percentage remained above 90%, even after five cycles under visible irradiation. The photocatalytic dye degradation mechanism employed by α/β-Bi2O3 was proposed based on active species trapping experiments.