Construction of a novel Ca2Bi2O5/α-Bi2O3 semiconductor heterojunction for enhanced visible photocatalytic application

Bi3+-containing compounds have been intensively investigated for their potential application as photocatalysts for degrading pollutants and splitting water. In this work, a Ca2Bi2O5/alpha-Bi2O3 heterojunction photocatalyst was successfully prepared via the facile sol-gel method. The excess of the initial Bi raw material can result in the Ca2Bi2O5/alpha-Bi2O3 heterojunction of the final products. The as-synthesized nanoparticles were investigated via Xray diffraction, transmission electron microscopy, scanning electron microscopy, energy-dispersive spectrometry, UV-Vis optical absorption, and X-ray photoelectron spectroscopy. The band energy of the Ca2Bi2O5 substrate semiconductor was 2.49 eV and characterized with a direct transition nature. The photocatalytic effect on the photodegradation of Rhodamine B solutions was evaluated. Ca2Bi2O5/alpha-Bi2O3 heterojunctions showed improved photocatalytic abilities compared with single Ca2Bi2O5 and alpha-Bi2O3 under viable light irradiation. The mechanism was discussed in terms of the microstructure, luminescence intensities, and decay curves (lifetimes). The photo-produced electrons and holes can be adequately separated in Ca2Bi2O5/alpha-Bi2O3 heterojunctions ensuring its photocatalytic activities. The present results can serve as reference for investigating the optical properties of Bi semiconductors.