Abstract
Rare earth (R) ion-doped TiO2 nanocomposites (NCs) with general composition (R: Y, Yb, Gd; , 0.2) were synthesized through co-precipitation/hydrolysis (CPH). NC particles with average size of approximately a few tens of nm were obtained. Similar compositions of polycrystalline (PC) samples with larger particle size were also prepared employing solid state reaction (SSR) method. Visible light photocatalytic activity of all samples was investigated for degradation of Congo red (CR) dye. Both in terms of apparent rate constant () and percent degradation after 180 min (), all NCs produced significantly enhanced degradation as compared to pure TiO2 and PC samples. Best degradation of 95% ( value) resulted with composition of Y3+ doped NC with min−1. This was followed by of 85 and 80%, produced with Yb3+ and Gd3+ doped, NCs, at around and min−1, respectively. The observations clearly suggest that enhanced photocatalytic degradation of CR is directly related to smaller particle size of the catalysts. Moreover, the presence of rare earth ions in the composites facilitates further improvement of degradation efficiency through effective suppression of recombination.
Highlights
Among several applications associated with titanium dioxide (TiO2), photocatalysis is perhaps the most important one [1, 2]
In this article, which is essentially an extension of our previous work, we report, for the very first time, the results of visible light-induced photocatalytic degradation of Congo red (CR) under the influence of Yb+- and Gd3+-doped, nanosized TiO2 photocatalysts
Sharper peaks obtained with the PC samples correspond to more crystalline structure and larger particle size
Summary
Among several applications associated with titanium dioxide (TiO2), photocatalysis is perhaps the most important one [1, 2]. Once the catalyst surface is covered, effectively the colour of the latter determines the required excitation wavelength, making the visible light induced photocatalysis possible It is noteworthy, that at very small particle dimensions, e−/h+ recombination could become significantly high owing. We have already reported as high as 95% degradation of the dye Congo red (CR) in 180 min and a reasonably high rate of 2.74 × 10−2 min−1, with TiO2 NCs doped with 0.2 and 0.1 molar concentration of Y3+ ions, respectively [5] With these encouraging results and the background mentioned previously, it was crucial to investigate the performance of TiO2 photocatalysts doped with other rare earth ions. We present the results in comparison to those obtained earlier with similar NCs doped with Y3+ ions [5] and discuss the effects of particle size
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