High nuclearity Co polyoxometalate based artificial photosynthesis for solar hydrogen generation

The photocatalytic hydrogen (H2) generation by the high nuclearity Co substituted polyoxometalates (POMs), K10Na12[{Co3(B-β-SiW9O33(OH))(B-β-SiW8O29 (OH)2)}2]·49H2O (abbreviated as CoPOM) was reported. Owing to the multielectron redox capabilities of the high nuclearity CoPOM, the POM showed excellent photocatalytic activities toward H2 evolution in both molecule scale (homogeneous) and composite (heterogeneous) systems. The photocatalytic activities of CoPOM were much better than H3PW12O40. UV–Vis–NIR absorption spectral, Raman spectral, cyclic voltammetric behavior and intermittent photoelectrochemical current response were used to characterize the structure of the TiO2/CoPOM composite and interaction between TiO2 and CoPOM. Analogous “Z-scheme” and “dye” sensitized mechanisms were proposed for the homogeneous and heterogeneous systems toward photocatalytic H2 evolution under solar light irradiation, respectively.