Artificial photosynthesis for solar hydrogen generation over transition-metal substituted Keggin-type titanium tungstate

The photocatalytic hydrogen (H-2) evolution with transition-metal substituted Keggin-type titanium tungstates Na-5(6)[MTiW11O39]center dot xH(2)O (abbreviated as TiW11M (M = Fe, Co, Zn)) as photocatalyst was reported. They showed good photocatalytic activities toward H-2 evolution in homogeneous systems under simulated solar light irradiation. The order of photocatalytic activity was TiW11Co approximate to TiW11Zn > TiW11Fe >> H3PW12O40 (PW12). The selected POMs showed good stability during the reactions. Karl Fischer analysis, ICPE (Inductive Coupled Plasma Emission) and FT-IR (Fourier Transform Infrared Spectroscopy) were used to confirm the composition and structure. UV-Vis absorption spectra, kinetics investigation and cyclic voltammetric characterizations were used to explain the photocatalytic results. Finally, an analogous "Z-scheme'' mechanism was proposed for the homogeneous systems toward photocatalytic H-2 evolution under simulated solar light irradiation.