Heterogeneous photocatalytic water reduction using a QD-cluster pentacobalt polyoxotungstate complex

Abstract

An efficient novel photo-driven water reduction catalyst was reported by using the quantum dot cluster pentacobalt polyoxotungestate complex Cs₁₂[Co₃W(H₂O)₂(CoW₉O₃₄)₂]·H₂O which was prepared by self-assembly of the corresponding sodium salt as the precursor. This water reduction catalyst was hydrolytically stable and synthesized by a sonochemical method with Triton-X-100 as a surfactant using earth abundant elements (Co, W, and O) and characterized by different methods such as FTIR, UV-vis, TGA, TEM, elemental analysis and an electrochemical study. This catalyst shows an excellent catalytic current on the cyclic voltammetry time scale and produces hydrogen under mild conditions. [Ru(bpy)₃]²⁺ (bpy = 2,2′-bipyridine) was used as the photosensitizer (PS), methyl viologen (MV) as an electron relay reagent and EDTA as a sacrificial electron donor. The quantum efficiency reached 12.1% for H₂ production at pH 4.8 under visible light irradiation which is significantly high. Besides, it was stable and reused under catalytic turnover conditions five times without a decrease in activity.