Rapid preparation of α, β-Bi2O3 and α/β-Bi2O3 heterojunction with enhanced photocatalytic properties

α-Bi2O3 and β-Bi2O3 nanoparticles were selectively synthesized via one-step solution combustion synthesis (SCS) using bismuth nitrate (Bi(NO3)3·5H2O) as the oxidant and tartaric acid (C4H6O6) as the fuel, and α/β-Bi2O3 heterojunction was rapidly prepared by treating SCS β-Bi2O3 powders with NaOH solution. The physical and chemical properties of as-prepared samples were characterized by XRD, SEM, TEM, PL, and UV-vis techniques. The formation of α/β-Bi2O3 heterojunction can be proven by TEM, UV-vis diffuse reflectance spectra, and PL spectra results. The band gap energies of α-Bi2O3, β-Bi2O3, and α/β-Bi2O3 measured by UV-vis diffuse reflectance spectra were estimated to be about 2.9, 2.48, and 2.7 eV, respectively. The PL spectra of α/β-Bi2O3 heterojunction showed higher efficiency of charge separation and transfer across the α–β phase junction than those of α-Bi2O3 and β-Bi2O3, leading to the enhancement of photocatalytic activity. The synthesized α/β-Bi2O3 heterojunction can degrade 86% of rhodamin B (RhB) after 180 min under visible-light irradiation, better than those of pure α-Bi2O3 (24%, 180 min) and pure β-Bi2O3 (60%, 180 min). Consequently, α/β-Bi2O3 heterojunction is a promising photocatalyst, which can be easily prepared by SCS and post-treatment of NaOH solution.