Visible light photocatalysis by a Titania-Rhodium(III) complex

Titania hybrid photocatalysts containing 0.5, 1.0, 2.0, and 5.0 wt% of rhodium(III) were prepared by chemisorption of RhCl3 x 3H(2)O onto anatase hydrate powder (TH). Analytical data suggest that a titania-trichlororhodate complex is produced containing a [TiO2]-O-Rh bond. Similar results are found in the case of modification by RhBr3 x 3H(2)O. Diffuse reflectance spectra exhibit an absorption shoulder throughout the visible region down to 700 nm. Photoelectrochemical measurements indicate that the quasi-Fermi level of electrons is gradually shifted to more anodic potentials with increasing rhodium loading reaching a value of -0.34 V at pH 7 (vs. NHE) in the case of 5.0%RhCl3/TH. This is more anodic by 210 mV as compared to unmodified TH. Upon visible light irradiation this photocatalyst induces a fast mineralization of 4-chlorophenol whereas cyanuric acid, which is known to be mineralized in the presence of the analogous Pt(IV) modified titania, is not degraded. (C) 2008 Elsevier B.V. All rights reserved.