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.
This study demonstrates that bio-based products of lignin depolymerisation can potentially replace common antioxidants and UV absorbers in the plastics and cosmetics industries. The kraft lignin Indulin AT was used to obtain low-MW lignin and monomers & oligomers rich in phenolic hydroxyl groups. Both thermo-oxidative stability and antioxidant activity significantly improved upon lignin depolymerisation. The results from oxidation induction time differential scanning calorimetry (OIT-DSC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) measurements show that the lignin based depolymerisation products are comparable with commercial antioxidants like pentaerythritol-tetrakis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate) (Irganox 1010). UV/vis spectroscopy was investigated to confirm absorption of the depolymerisation products in the UVA and UVB range (280–400 nm).
This work investigates the photoinduced energy transfer from poly(N-vinylcarbazole) (PVK), as a donor material, to fac-(2,2'-bipyridyl)Re(CO)3Cl, as a catalyst acceptor, for its potential application towards CO2 reduction. Photoluminescence quenching experiments reveal dynamic quenching through resonance energy transfer in solid donor/acceptor mixtures and in solid/liquid systems. The bimolecular reaction rate constant at solution–film interfaces for the elementary reaction of the excited state with the quencher material could be determined as 8.8(±1.4)×1011 L mol−1 s−1 by using Stern–Volmer analysis. This work shows that PVK is an effective and cheap absorber material that can act efficiently as a redox photosensitizer in combination with fac-(2,2'-bipyridyl)Re(CO)3Cl as a catalyst acceptor, which might lead to possible applications in photocatalytic CO2 reduction.
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