Organometallic Rhodium(III) Complexes as Catalysts for the Photoreduction of Protons to Hydrogen on Colloidal TiO2

The photoreduction of H + to H 2 by sunlight and colloidal TiO 2 in the presence of the rhodium(III) complexes 1 (ppy = oligopyridine ligand, e.g., bipyridyl; L=H 2 O, Cl ⊖ , Br ⊖ , I ⊖ ; n = 1, 2) is possible without the participation of colloidal platinum and is not restricted to alkaline solution. The complexes are thereby reduced, via the Rh II stage, to Rh I complexes, which then undergo transformation to the Rh III complexes with evolution of hydrogen. The course of the reaction was investigated by cyclic voltammetry and pulse radiolysis as well as by transient absorption spectroscopy. equation image