Binuclear polyoxometalates based on abundant metals as efficient homogeneous photocatalytic water oxidation catalysts

Abstract

The exploration of efficient, stable and cheap water oxidation catalysts (WOCs) is essential for overcoming the bottleneck of water splitting. A series polyoxometalates (POMs) based dinuclear clusters, [M2(β-SiW8O31)2]16− (M=Co2+, Ni2+, Cu2+ and Zn2+) are reported as efficient, robust visible light-driven water oxidation catalysts for the first time. The quite high catalytic turnover number (TON 925), turnover frequency (TOF 7.0s−1) and 24% quantum yield of [Co2(β-SiW8O31)2]16− (Co-POM) for oxygen evolution are achieved at pH 9.0 using [Ru(bpy)3]2+ as photosensitizer and persulfate as sacrificial electron acceptor. Various experiments including laser flash photolysis, X-ray photoelectron spectra (XPS), UV–vis spectra and IR confirm that Co-POM is the dominant catalyst during water oxidation process. The results offer a utile insight into the design of water oxidation catalysts.