Synthesis of β-Bi2O3 towards the application of photocatalytic degradation of methyl orange and its instability

•Synthesis of Bi2O2CO3 and its conversion to phase pure β-Bi2O3.•Pure β-Bi2O3 degrades larger amount of methyl orange compared to Bi2O2CO3.•Pseudo first order kinetics fits well with higher correlation coefficient.•Conversion of Bi2O3 to Bi2O2CO3 after photocatalytic degradation proves instability.

Bismuth oxide carbonate was synthesized from bismuth nitrate and potassium carbonate and then converted to phase pure β-Bi2O3 form by means of thermal decomposition. X-ray diffraction, HR-SEM, diffuse reflectance UV–vis and photocatalytic degradation studies were carried out on both the samples. Bi2O2CO3 exhibited a wide band gap of 3.406(5) eV while β-Bi2O3 had a lesser band gap of 2.589(3) eV. β-Bi2O3 degrades a higher amount of methyl orange because of its lesser band gap and its optimum loading was 0.1 g in 50 ml of 10 ppm solution. After photocatalytic degradation Bi2O2CO3 remains in the stable form whereas β-Bi2O3 changes to Bi2O2CO3.