Homogeneous Cobalt/Vanadium Complexes as Precursors for Functionalized Mixed Oxides in Visible-Light-Driven Water Oxidation.

The heterometallic complexes (NH ) [Co(H O) ] [V O ]⋅4 H O (1) and (NH ) [Co(H O) (β-HAla)] [V O ]⋅4 H O (2) have been synthesized and used for the preparation of mixed oxides as catalysts for water oxidation. Thermal decomposition of 1 and 2 at relatively low temperatures (<500 °C) leads to the formation of the solid mixed oxides CoV O /V O (3) and Co V O /V O (4). The complexes (1, 2) and heterogeneous materials (3, 4) act as catalysts for photoinduced water oxidation. A modification of the thermal decomposition procedure allowed the deposition of mixed metal oxides (MMO) on a mesoporous TiO film. The electrodes containing Co/V MMOs in TiO films were used for electrocatalytic water oxidation and showed good stability and sustained anodic currents of about 5 mA cm at 1.72 V versus relative hydrogen electrode (RHE). This method of functionalizing TiO films with MMOs at relatively low temperatures (<500 °C) can be used to produce other oxides with different functionality for applications in, for example, artificial photosynthesis.