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

The heterometallic complexes (NH4)(2)[Co(H2O)(6)](2)[V10O28]4H(2)O (1) and (NH4)(2)[Co(H2O)(5)(-HAla)](2)[V10O28]4H(2)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 degrees C) leads to the formation of the solid mixed oxides CoV2O6/V2O5 (3) and Co2V2O7/V2O5 (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 TiO2 film. The electrodes containing Co/V MMOs in TiO2 films were used for electrocatalytic water oxidation and showed good stability and sustained anodic currents of about 5mAcm(-2) at 1.72V versus relative hydrogen electrode (RHE). This method of functionalizing TiO2 films with MMOs at relatively low temperatures (<500 degrees C) can be used to produce other oxides with different functionality for applications in, for example, artificial photosynthesis.