Photoelectrochemical Reduction of CO₂Using Third-Generation Conjugated Polymers

Abstract

Third-generation polythiophenes, bearing Rhenium carbonyl complexes and pyridinium as pendant active sites were used to drive the photoelectrochemical reduction of CO 2 . Cyclic voltammetry and controlled potential electrolysis experiments were performed in CO 2 -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~20. In the case of poly-[4-(7-(thiophen-3-yl)heptyl)pyridine] which was supposed to catalyse reduction reaction of CO 2 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.

Organic, Organometallic and Bioorganic Catalysts for Electrochemical Reduction of CO2

“…[113] Apaydin et al investigated polythiophene structures with pendantc atalyst groups for the photoelectrochemicalr eduction of CO 2 . [114] This is of particulari nterest because previous studies addressing the use of conjugated polymers lacked the information on how ap -type materialc an drive electrons through its backbone unlesst unneling wast he main driving force. [Re(bpy)(CO) 3 Cl] was attached to thiophenea tt he 3-position through an alkyl chain [3HRe(bpy)(CO) 3 Cl-Th] and then electrochemically polymerized in the presenceo fb oron trifluorided iethyle therate to yield poly[3HRe(bpy)(CO) 3 Cl-Th] (Figure 24).…”

“…The authors reachedaf aradaic efficiency of 2.5 %a nd aT ON of 20 which was calculated from the estimated active sites on the surface. [114] It is explained in the study that the low faradaic efficiency can be attributed to surface limited reactivity and the choice of ah ole extractinge lectrode.H owever, this is one of the very few studies where the use of an organic semiconducting polymer and its light absorbing properties to drive photoelectrochemical reduction of CO 2 is shown.…”

“…Cyclic voltammogramdemonstratingt he potentiodynamic polymerization of [3HRe(bpy)(CO)3 Cl-Th]. Inset:Photo of at hick film of the polymer.Reproduced with permission from Ref [114]…”

“…H 2 can be observed as ap roduct if the electrolyte medium is protic. F denotesthe catalystfunctionalization on the polymer.Reproducedw ith permissionfrom Ref [114]…”

Photoelectrocatalytic Reduction of CO2 into C1 Products by Using Modified‐Semiconductor‐Based Catalyst Systems

“…Very recently,t he efficacy of such as trategy was exploredb y Apaydine tal.,w ho used at hird-generation polythiophene as the polymericb ackbone, owing to its low air and moisture sensitivities. [29] Upon illumination, polythiophene can actively serve as an n-type charge transporter and perform electron transfer,t hus leading to CO 2 reduction.T he synthesis of the polymer poly[3HRe(bpy)(CO) 3 Cl-Th] was performed from monomeric units by using the electropolymerization technique. The synthesized polymer was placed inside the cathode chamber with Ag/AgCl as aq uasi-reference electrode and Pt was used as the counter anode.…”