COOLEFIN: Novel Dinuclear Late Transition Metal Catalysts for CO2/Olefin and CO2/Epoxide/olefin Copolymerization
- FB Chemie
|(2021): Cascade CO2 electroreduction enables efficient carbonate-free production of ethylene Joule. Cell Press. 2021, 5(3), pp. 706-719. eISSN 2542-4351. Available under: doi: 10.1016/j.joule.2021.01.007
CO2 electroreduction provides a route to convert waste emissions into chemicals such as ethylene (C2H4). However, the direct transformation of CO2-to-C2H4 suffers from CO2 loss to carbonate, consuming up to 72% of energy input. A cascade approach—coupling a solid-oxide CO2-to-CO electrochemical cell (SOEC) with a CO-to-C2H4 membrane electrode assembly (MEA)—would eliminate CO2 loss to carbonate. However, this approach requires a CO-to-C2H4 MEA with energy efficiency well beyond demonstrations to date. Focusing on the MEA, we find that an N-tolyl substituted tetrahydro-bipyridine film improves the stabilization of key reaction intermediates, while an SSC ionomer enhances CO transport to the Cu surface, enabling a C2H4 faradaic efficiency of 65% at 150 mA cm−2 for 110 h. Demonstrating a cascade SOEC-MEA approach, we achieve CO2-to-C2H4 with a ~48% reduction in energy intensity compared with the direct route. We further reduce the energy intensity by coupling CO electroreduction (CORR) with glucose electrooxidation.
|(2021): Dramatic HER Suppression on Ag Electrodes via Molecular Films for Highly Selective CO2 to CO Reduction ACS Catalysis. ACS Publications. 2021, 11(8), pp. 4530-4537. eISSN 2155-5435. Available under: doi: 10.1021/acscatal.1c00338
Dramatic HER Suppression on Ag Electrodes via Molecular Films for Highly Selective CO2 to CO Reduction
The carbon dioxide reduction reaction (CO2RR) in aqueous electrolytes suffers from efficiency loss due to the competitive hydrogen evolution reaction (HER). Developing efficient methods to suppress HER is a crucial step toward CO2 utilization. Herein we report the selective conversion of CO2 to CO on planar silver electrodes with Faradaic efficiencies >99% using simple pyridinium-based additives. Similar to our previous studies on copper electrodes, the additives form an organic film which alters CO2RR selectivity. We report electrochemical kinetic and other mechanistic data to shed light on the role of these organic layers in suppressing HER. These data suggest that hydrogen production is selectively inhibited by the growth of a hydrophobic organic layer on the silver surface that limits proton but not CO2 mass transport at certain applied potentials. The data also point to the involvement of a proton-transfer within the rate-determining step of the catalysis, instead of the commonly observed electron-transfer step for the case of planar Ag electrodes.
|(2020): Molecular enhancement of heterogeneous CO2 reduction Nature Materials. Springer Nature. 2020, 19(3), pp. 266-276. ISSN 1476-1122. eISSN 1476-4660. Available under: doi: 10.1038/s41563-020-0610-2
The electrocatalytic carbon dioxide reduction reaction (CO2RR) addresses the need for storage of renewable energy in valuable carbon-based fuels and feedstocks, yet challenges remain in the improvement of electrosynthesis pathways for highly selective hydrocarbon production. To improve catalysis further, it is of increasing interest to lever synergies between heterogeneous and homogeneous approaches. Organic molecules or metal complexes adjacent to heterogeneous active sites provide additional binding interactions that may tune the stability of intermediates, improving catalytic performance by increasing Faradaic efficiency (product selectivity), as well as decreasing overpotential. We offer a forward-looking perspective on molecularly enhanced heterogeneous catalysis for CO2RR. We discuss four categories of molecularly enhanced strategies: molecular-additive-modified heterogeneous catalysts, immobilized organometallic complex catalysts, reticular catalysts and metal-free polymer catalysts. We introduce present-day challenges in molecular strategies and describe a vision for CO2RR electrocatalysis towards multi-carbon products. These strategies provide potential avenues to address the challenges of catalyst activity, selectivity and stability in the further development of CO2RR.
|(2020): Molecular tuning of CO2-to-ethylene conversion Nature. Springer Nature. 2020, 577(7791), pp. 509-513. ISSN 0028-0836. eISSN 1476-4687. Available under: doi: 10.1038/s41586-019-1782-2
The electrocatalytic reduction of carbon dioxide, powered by renewable electricity, to produce valuable fuels and feedstocks provides a sustainable and carbon-neutral approach to the storage of energy produced by intermittent renewable sources1. However, the highly selective generation of economically desirable products such as ethylene from the carbon dioxide reduction reaction (CO2RR) remains a challenge2. Tuning the stabilities of intermediates to favour a desired reaction pathway can improve selectivity3-5, and this has recently been explored for the reaction on copper by controlling morphology6, grain boundaries7, facets8, oxidation state9 and dopants10. Unfortunately, the Faradaic efficiency for ethylene is still low in neutral media (60 per cent at a partial current density of 7 milliamperes per square centimetre in the best catalyst reported so far9), resulting in a low energy efficiency. Here we present a molecular tuning strategy-the functionalization of the surface of electrocatalysts with organic molecules-that stabilizes intermediates for more selective CO2RR to ethylene. Using electrochemical, operando/in situ spectroscopic and computational studies, we investigate the influence of a library of molecules, derived by electro-dimerization of arylpyridiniums11, adsorbed on copper. We find that the adhered molecules improve the stabilization of an 'atop-bound' CO intermediate (that is, an intermediate bound to a single copper atom), thereby favouring further reduction to ethylene. As a result of this strategy, we report the CO2RR to ethylene with a Faradaic efficiency of 72 per cent at a partial current density of 230 milliamperes per square centimetre in a liquid-electrolyte flow cell in a neutral medium. We report stable ethylene electrosynthesis for 190 hours in a system based on a membrane-electrode assembly that provides a full-cell energy efficiency of 20 per cent. We anticipate that this may be generalized to enable molecular strategies to complement heterogeneous catalysts by stabilizing intermediates through local molecular tuning.
|01.01.2019 – 31.12.2021