Effect of fuels on the physicochemical properties and photocatalytic activity of bismuth oxide, synthesized using solution combustion method

Abstract

The potential of bismuth oxide (Bi2O3) as a photocatalyst, due to its a wide band gap (2.3-3.3 eV), was successfully synthesized using the solution combustion method with several fuels: urea, glycine, and citric acid. The synthesis was started by dissolving bismuth nitrate pentahydrate in nitric acid and then adding the fuel. The solution formed was heated for 8 h at 300°C. After heating, calcination was carried out for 4 h at 700°C. The resulting three products were in a yellow powder form. Fourier Transform InfraRed (FTIR) spectra of the samples confirmed that Bi2O3 had formed, as indicated by the functional groups of Bi-O-Bi observed at approximately 830-850 cm-1 and Bi-O at 1380 cm-1. X-ray diffractograms indicated that Bi2O3 synthesized using urea and glycine fuels was present in the mixed phases of α-Bi2O3 at 2θ of 27.7, 33.3, 27.2 and β-Bi2O3 at 2θ of 30.5, 41.8, 45.5, based on the Joint Committee on Powder Diffraction Standards (JCPDS) database 41-1449 and 27-0050, respectively. However, Bi2O3 produced by citric acid fuel comprised only α-Bi2O3. Furthermore, different fuels produced different crystallite product sizes; urea generated the smallest crystallite, followed by glycine and citric acid. Additionally, the photocatalytic activity on the degradation of methyl orange of Bi2O3 synthesized using urea fuel exhibited better photocatalytic activity than the other products, with degradation rate constants of 4.38x10-5 s-1, 3.38x10-5 s-1, 2.33x10-5 s-1 for bismuth oxide synthesized by urea, glycine, and citric acid, respectively.