Photoelectrochemical Reduction of CO2 Using Third-Generation Conjugated Polymers

Third-generation polythiophenes, bearing Rhenium carbonyl complexes and pyridinium as pendant active sites were used to drive the photoelectrochemical reduction of CO2. Cyclic voltammetry and controlled potential electrolysis experiments were performed in CO2-saturated acetonitrile, acetonitrile-water and aqueous solutions under illumination as well as in dark. The formation of CO was confirmed with IR spectroscopy and quantified with gas chromatography in the case of poly-[Re-(4-methyl-4'-(7-(thiophen-3-yl) heptyl)-2,2'-bipyridyl) tricarbonylchloride] giving a max. Faradaic efficiency of 2.5% and a Turnover number of similar to 20. In the case of poly-[4-(7-(thiophen-3-yl) heptyl) pyridine] which was supposed to catalyse reduction reaction of CO2 to MeOH, no products were observed. Although the initial efficiencies are not high due to the surface limited processes, this immobilization of such catalysts on the photoelectrode might be industrially attractive.