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

Abstract

The photocatalytic hydrogen (H₂) evolution with transition-metal substituted Keggin-type titanium tungstates Na₅₍₆₎[MTiW₁₁O₃₉]·xH₂O (abbreviated as TiW₁₁M (M = Fe, Co, Zn)) as photocatalyst was reported. They showed good photocatalytic activities toward H₂ evolution in homogeneous systems under simulated solar light irradiation. The order of photocatalytic activity was TiW₁₁Co ≈ 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 H₂ evolution under simulated solar light irradiation.