Titanium dioxide (titania) is a widely-studied photocatalyst. Prior investigations have examined the ultraviolet photodecomposition of methanol on titania using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). In the current study, methanol was used as a probe molecule to examine the effects of added cerium oxide (ceria) on the ultraviolet surface photochemistry of titania. Titania was decorated with different amounts of cerium oxide using deposition precipitation with cerium (III) nitrate as the cerium oxide precursor and titania P25 as the substrate. A series of decorated titania materials were prepared, with weight loadings predicted to develop surface coverages of approximately 0.25, 0.5, 1, and 2 monolayers of cerium (IV) species. XRD results confirmed that the 0.25 and 0.5 monolayer samples contained no crystallites corresponding to cerium oxide species, while the 1 and 2 monolayer materials contained CeO2 crystallites with sizes on the order of 4 nm. The dried and calcined solids were placed in the DRIFTS reaction cell and a mixture of methanol in N2 (1:1000) flowed through the solid powder to create the adsorbed methanol species. Strong peaks due to CH3 infrared absorption were observed at approximately 2830, 2850, 2930, and 2950 cm-1, corresponding to physisorbed methanol as well as methoxy (chemisorbed methanol) species. After adsorption of methanol, bare and decorated titania solids were then exposed to ultraviolet light in the presence of oxygen, and the integrated area of the CH3 infrared absorption band before and after irradiation was used as a measure of the decomposition. The bare titania, 0.5, and 1 monolayer samples lost 40-60% of the CH3 integrated intensity after UV irradiation whereas the 0.25 and 2 monolayer samples lost 82% and 99%, respectively. These results as well as those from flow reactor studies and the intensity dependence studies to gain further insight into the nature of the modified surface reactivity.

Enhanced photodecomposition activity induced by nanodimensional cerium oxide domains on titania surfaces

249th National Meeting (2015)

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