High nuclearity Co polyoxometalate based artificial photosynthesis for solar hydrogen generation

•Multielectron redox capabilities of the high nuclearity CoPOM.•Excellent photocatalytic H2 generation activities of the high nuclearity CoPOM.•Analogous “Z-scheme” and “dye” sensitized mechanisms for CoPOM and TiO2/CoPOM.

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.

Graphical abstractThe high nuclearity K10Na12[{Co3(B-β-SiW9O33(OH))(B-β-SiW8O29(OH)2)}2]·49H2O (abbreviated as CoPOM) formed by the combination of several polyanion units shows excellent photocatalytic activities toward H2 evolution from molecule scale to composite systems. Analogous “Z-scheme” and “dye” sensitized catalytic mechanisms have been proposed for molecule scale and composite systems, respectively.Figure optionsDownload full-size imageDownload as PowerPoint slide