Laser induced selective photo-catalytic reduction of CO 2 into methanol using In 2 O 3 -WO 3 nano-composite

Abstract

Abstract Tungsten oxide is a photo-catalyst well known for many photo catalytic applications, is found to be completely inactive in the photo catalytic process of converting carbon dioxide into methanol. Tungsten oxide was made effective for this photo catalytic process by forming a composite with indium dioxide and this tungsten oxide/indium dioxide nanocomposite, in conjunction with the laser radiation of 355 nm wavelength initiated and catalyzed the reaction to give the methanol production yield as high as 496 μmol g −1 h −1 . The maximum quantum and conversion efficiencies calculated for this photochemical process after 60 min of irradiation are 2.25% and 12% respectively which is quite considerable compared to earlier reports. A reduced electron–hole recombination observed from the photoluminescence spectra was instrumental in the effectiveness of tungsten oxide/indium dioxide nanocomposite in this particular photo catalytic process despite the decrease in the UV–vis light absorption of the material revealed in the absorption spectra. The observed reduction in the electron hole combination can be attributed to the spatial charge separation that takes place in the type–II heterojunction formed between tungsten oxide and indium dioxide. Optical studies also revealed the broadening of the band gap energy of the tungsten oxide/indium dioxide nanocomposite compared to nano tungsten oxide. In addition to the optical studies, XRD, FESEM and XPS analysis of the composite material were also carried out.