Photocatalytic Activities of Bi2O3, WO3, and Fe2O3: An Assessment through Decomposition of Peroxomonosulfate in Visible Radiation

Abstract Bi2O3 semiconductor powder (Eg=2.8–2.9 eV) was chosen for the first time to effect photocatalysis and was found to decompose peroxomonosulfate (PMS) with visible light of λ>400 nm. Doping of Bi2O3 with Cu(II)-ion considerably enhanced the photocatalytic efficiency. The effects of variation of (i) the [dopant] in Cu(II)/Bi2O3, (ii) the catalyst amount, and (iii) the initial [PMS] on the rate of decomposition of PMS were investigated. It was observed that (a) 4 atomic % was the optimum [dopant] for Cu(II)/Bi2C3, (b) the rate increased linearly with increase in catalyst amount, and (c) the decomposition of PMS followed a Langmuir kinetics in the concentration range, [PMS]0=0.5–3.0×10−3 mol dm−3. A suitable reaction mechanism is proposed for the decomposition of PMS involving all the possible reactions. A comparative analysis of the photocatalytic activities of undoped and Cu(II)-doped Bi2O3, WO3, and Fe2O3 indicated that Cu(II)-doping enhances the activity of Bi2O3 to a greater extent than those observed with the other two semiconductors. This photocatalytic decomposition of PMS is one of the examples of visible light assisted reaction which otherwise takes place under UV radiation (λ≤280 nm) only.