Effect of Nd2O3 addition on the surface phase of TiO2 and photocatalytic activity studied by UV Raman spectroscopy

TiO2 modified with Nd2O3 (Nd–TiO2) nanoparticles were prepared by a co-precipitation method and utilized as the photocatalysts for the degradation of Rhodamine B (RhB). The influence of Nd2O3 on the bulk and surface phase, surface area, particle size, and optical response of TiO2 was investigated by X-ray diffraction (XRD), UV Raman spectroscopy, transmission electron microscopy (TEM), BET, and UV–visible diffuse reflectance spectra. It is found that the crystalline phase and phase composition in the bulk and surface region of Nd–TiO2 calcined at high temperatures can be tuned by changing the amount of Nd2O3. Based on the results from XPS, EDX, XRD, and UV Raman spectra, it is assumed that Nd3+ ions do not enter the TiO2 lattice, but highly disperse onto the Nd–TiO2 particle surface in the form of Nd2O3 crystallites. These crystallites inhibit the agglomeration, growth in crystal size, and anatase-to-rutile phase transformation of TiO2. In the photocatalytic degradation of RhB reaction, Nd–TiO2 nanoparticles with higher surface area and wider optical response are more reactive in case of the same surface anatase phase. When the mixed phases of anatase and rutile exist in the surface region of Nd–TiO2, the synergetic effect over surface area and optical response is the important parameter which determines optimal photocatalytic activity.

► The crystalline phase and phase composition in the bulk and surface region of the Nd–TiO2 sample calcined at high temperature can be easily tuned by changing the amount of Nd2O3. ► Nd3+ ions do not enter the TiO2 lattice, but highly disperse onto the Nd–TiO2 particle surface in the form of Nd2O3 crystallites. ► These crystallites inhibit the agglomeration, growth in crystal size, and anatase-to-rutile phase transformation of TiO2. ► In photocatalytic degradation of RhB reaction, Nd–TiO2 nanoparticles with higher surface area and wider optical response are more reactive in case of the same surface anatase phase. ► When the mixed phases of anatase and rutile exist in the surface region of Nd–TiO2, the synergetic effect over surface area and optical response is the important parameter which determines optimal photocatalytic activity of degradation of RhB.