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- ItemElectrocatalytic Reduction of CO2 to Acetic Acid by a Molecular Manganese Corrole Complex(Weinheim : Wiley-VCH, 2020) De, Ratnadip; Gonglach, Sabrina; Paul, Shounik; Haas, Michael; Sreejith, S.S.; Gerschel, Philipp; Apfel, Ulf-Peter; Vuong, Thanh Huyen; Rabeah, Jabor; Roy, Soumyajit; Schöfberger, WolfgangThe controlled electrochemical reduction of carbon dioxide to value added chemicals is an important strategy in terms of renewable energy technologies. Therefore, the development of efficient and stable catalysts in an aqueous environment is of great importance. In this context, we focused on synthesizing and studying a molecular MnIII-corrole complex, which is modified on the three meso-positions with polyethylene glycol moieties for direct and selective production of acetic acid from CO2. Electrochemical reduction of MnIII leads to an electroactive MnII species, which binds CO2 and stabilizes the reduced intermediates. This catalyst allows to electrochemically reduce CO2 to acetic acid in a moderate acidic aqueous medium (pH 6) with a selectivity of 63 % and a turn over frequency (TOF) of 8.25 h−1, when immobilized on a carbon paper (CP) electrode. In terms of high selectivity towards acetate, we propose the formation and reduction of an oxalate type intermediate, stabilized at the MnIII-corrole center. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemHighly active and selective photochemical reduction of CO2 to CO using molecular-defined cyclopentadienone iron complexes(Cambridge : Soc., 2015) Rosas-Hernández, Alonso; Alsabeh, Pamela G.; Barsch, Enrico; Junge, Hernrik; Ludwig, Ralf; Beller, MatthiasHerein, we report highly active (cyclopentadienone)iron–tricarbonyl complexes for CO2 photoreduction using visible light with an Ir complex as photosensitizer and TEOA as electron/proton donor. Turnover numbers (TON) of ca. 600 (1 h) with initial turnover frequencies (TOF) up to 22.2 min−1 were observed. Operando FTIR measurements allowed for the proposal of a plausible mechanism for catalyst activation.
- ItemTowards a methanol economy based on homogeneous catalysis: methanol to H2 and CO2 to methanol(Cambridge : Soc., 2015) Alberico, E.; Nielsen, M.The possibility to implement both the exhaustive dehydrogenation of aqueous methanol to hydrogen and CO2 and the reverse reaction, the hydrogenation of CO2 to methanol and water, may pave the way to a methanol based economy as part of a promising renewable energy system. Recently, homogeneous catalytic systems have been reported which are able to promote either one or the other of the two reactions under mild conditions. Here, we review and discuss these developments.
- ItemSteering carbon dioxide reduction toward C–C coupling using copper electrodes modified with porous molecular films([London] : Nature Publishing Group UK, 2023) Zhao, Siqi; Christensen, Oliver; Sun, Zhaozong; Liang, Hongqing; Bagger, Alexander; Torbensen, Kristian; Nazari, Pegah; Lauritsen, Jeppe Vang; Pedersen, Steen Uttrup; Rossmeisl, Jan; Daasbjerg, KimCopper offers unique capability as catalyst for multicarbon compounds production in the electrochemical carbon dioxide reduction reaction. In lieu of conventional catalysis alloying with other elements, copper can be modified with organic molecules to regulate product distribution. Here, we systematically study to which extent the carbon dioxide reduction is affected by film thickness and porosity. On a polycrystalline copper electrode, immobilization of porous bipyridine-based films of varying thicknesses is shown to result in almost an order of magnitude enhancement of the intrinsic current density pertaining to ethylene formation while multicarbon products selectivity increases from 9.7 to 61.9%. In contrast, the total current density remains mostly unaffected by the modification once it is normalized with respect to the electrochemical active surface area. Supported by a microkinetic model, we propose that porous and thick films increase both local carbon monoxide partial pressure and the carbon monoxide surface coverage by retaining in situ generated carbon monoxide. This reroutes the reaction pathway toward multicarbon products by enhancing carbon–carbon coupling. Our study highlights the significance of customizing the molecular film structure to improve the selectivity of copper catalysts for carbon dioxide reduction reaction.
- ItemMicrobial respiration and natural attenuation of benzene contaminated soils investigated by cavity enhanced Raman multi-gas spectroscopy(Cambridge : Soc., 2015) Jochum, Tobias; Michalzik, Beate; Bachmann, Anne; Popp, Jürgen; Frosch, TorstenSoil and groundwater contamination with benzene can cause serious environmental damage. However, many soil microorganisms are capable to adapt and are known to strongly control the fate of organic contamination. Innovative cavity enhanced Raman multi-gas spectroscopy (CERS) was applied to investigate the short-term response of the soil micro-flora to sudden surface contamination with benzene regarding the temporal variations of gas products and their exchange rates with the adjacent atmosphere. 13C-labeled benzene was spiked on a silty-loamy soil column in order to track and separate the changes in heterotrophic soil respiration – involving 12CO2 and O2 – from the natural attenuation process of benzene degradation to ultimately form 13CO2. The respiratory quotient (RQ) decreased from a value 0.98 to 0.46 directly after the spiking and increased again within 33 hours to a value of 0.72. This coincided with the maximum 13CO2 concentration rate (0.63 μmol m−2 s−1), indicating the highest benzene degradation at 33 hours after the spiking event. The diffusion of benzene in the headspace and the biodegradation into 13CO2 were simultaneously monitored and 12 days after the benzene spiking no measurable degradation was detected anymore. The RQ finally returned to a value of 0.96 demonstrating the reestablished aerobic respiration.