Enhanced direct sunlight photocatalytic oxidation of methanol using nanocrystalline TiO2 calcined at different temperature
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The present study focused on photocatalytic oxidation of methanol to formaldehyde using nanocrystalline TiO2 (Degussa P-25) photocatalyst calcined at different temperature having different ratio of anatase (A)–rutile (R) phase composition under direct sunlight irradiation. The calcined nanocrystalline TiO2 was characterized using powder X-ray diffraction, N2 adsorption, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, and UV–Visible diffuse reflectance spectroscopy techniques. The determination of hydroxyl radical formation during the course of the reaction was carried out using fluorescence technique with terephthalic acid as a probe molecule. The photocatalytic activity of catalysts was evaluated by methanol oxidation under direct sunlight irradiation and activity was compared with pure anatase TiO2. The result revealed that nanocrystalline TiO2 (P-25) calcined at 500 °C displays higher photocatalytic activity and the order of rate of HCHO formation is P25-500 (A74 %:R26 %) > P25 (A80 %:R20 %) > AT (A100 %) > P25-600 (A12 %:R88 %) > P25-700 (R100 %). The result also infers that TiO2 with mixed phase exhibit higher photocatalytic activity than TiO2 with pure anatase or rutile phase. The rapid transfer of photogenerated electron from rutile to anatase leads to increase in the charge separation and enhances the photocatalytic activity under direct sunlight irradiation. Effect of operational parameters like amount of catalyst and effect of reaction atmosphere have been investigated on the photocatalytic oxidation of methanol under direct sunlight irradiation.
KeywordsPhotocatalysis Degussa P-25 TiO2 Calcination Phase composition Sunlight Methanol oxidation Formaldehyde
CSIR-CSMCRI Communication No. PRIS/154/2013. Authors are thankful to CSIR, New Delhi, India, for funding through Network Project on “Clean Coal Technologies (TapCoal)” (Project Number: CSC-0102). T S Natarajan thanks to CSIR, New Delhi for Senior Research Fellowship (File No: 31/28(162)/2012-EMR-I) and to AcSIR for enrolment in Ph.D. We also thankful to Analytical Discipline and Centralized Instrument Facility of the institute and Mr. Jayesh C. Chaudhari, Mr. Gopala Ram, Mr. V. K. Agarwal and Mr. K. Munusamy for kind support.
- Emeline AV, Smirnova LG, Kuzmin GN, Basov LL, Serpone N (2002) Spectral dependence of quantum yields in gas–solid heterogeneous photosystems: Influence of anatase/rutile content on the photostimulated adsorption of dioxygen and dihydrogen on titania. J Photochem Photobiol A 148:97–102CrossRefGoogle Scholar
- Ismail AA, Robben L, Bahnemann DW (2011) Study of the efficiency of UV and visible-light photocatalytic oxidation of methanol on mesoporous RuO2–TiO2 nanocomposites. Chem Phys Chem 12:982–991Google Scholar
- Nash T (1953) The colorimetric estimation of formaldehyde by means of the Hantzsch reaction. Biochem J 55:416–421Google Scholar
- Raj KJA, Viswanathan B (2009) Effect of surface area, pore volume and particle size of P25 titania on the phase transformation of anatase to rutile. Indian J Chem A 48:1378–1382Google Scholar
- Wang GH, Xu L, Zhang J, Yin T, Han D (2012) Enhanced photocatalytic activity of TiO2 powders (P25) via calcination treatment, Int J Photoenergy, Article ID 265760Google Scholar
- Yamashita H, Harada M, Misaka J, Takeuchi M, Ichihashi Y, Goto F, Ishida M, Sasaki T, Anpo M (2001) Application of ion beam techniques for preparation of metal ion-implanted TiO2 thin film photocatalyst available under visible light irradiation: metal ion-implantation and ionized cluster beam method. J Synchrotron Radiat 8:569–571CrossRefGoogle Scholar