CO2 electroreduction to ethylene via hydroxide-mediated copper catalysis at an abrupt interface
18 May 2018-Science (American Association for the Advancement of Science)-Vol. 360, Iss: 6390, pp 783-787
TL;DR: A copper electrocatalyst at an abrupt reaction interface in an alkaline electrolyte reduces CO2 to ethylene with 70% faradaic efficiency at a potential of −0.55 volts versus a reversible hydrogen electrode (RHE).
Abstract: Carbon dioxide (CO 2 ) electroreduction could provide a useful source of ethylene, but low conversion efficiency, low production rates, and low catalyst stability limit current systems. Here we report that a copper electrocatalyst at an abrupt reaction interface in an alkaline electrolyte reduces CO 2 to ethylene with 70% faradaic efficiency at a potential of −0.55 volts versus a reversible hydrogen electrode (RHE). Hydroxide ions on or near the copper surface lower the CO 2 reduction and carbon monoxide (CO)–CO coupling activation energy barriers; as a result, onset of ethylene evolution at −0.165 volts versus an RHE in 10 molar potassium hydroxide occurs almost simultaneously with CO production. Operational stability was enhanced via the introduction of a polymer-based gas diffusion layer that sandwiches the reaction interface between separate hydrophobic and conductive supports, providing constant ethylene selectivity for an initial 150 operating hours.
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20 Aug 2018
TL;DR: Jiao et al. as discussed by the authors presented a high-performance CO flow electrolyser with a well controlled electrode-electrolyte interface that can reach total current densities of up to 1'A'cm-2, together with improved C2+ selectivities.
Abstract: Carbon monoxide electrolysis has previously been reported to yield enhanced multi-carbon (C2+) Faradaic efficiencies of up to ~55%, but only at low reaction rates. This is due to the low solubility of CO in aqueous electrolytes and operation in batch-type reactors. Here, we present a high-performance CO flow electrolyser with a well controlled electrode–electrolyte interface that can reach total current densities of up to 1 A cm–2, together with improved C2+ selectivities. Computational transport modelling and isotopic C18O reduction experiments suggest that the enhanced activity is due to a higher surface pH under CO reduction conditions, which facilitates the production of acetate. At optimal operating conditions, we achieve a C2+ Faradaic efficiency of ~91% with a C2+ partial current density over 630 mA cm–2. Further investigations show that maintaining an efficient triple-phase boundary at the electrode–electrolyte interface is the most critical challenge in achieving a stable CO/CO2 electrolysis process at high rates. The low solubility of CO in aqueous electrolytes limits the implementation of CO electrolysers, since low current densities are typically achieved despite the fact that they deliver rather high Faradaic efficiencies to multi-carbon products. Now, Jiao and co-workers report a CO flow electrolyser with a well-controlled electrode–electrolyte interface that can achieve multi-carbon Faradaic efficiencies of 91% with a partial current density of 630 mA cm–2.
345 citations
342 citations
TL;DR: This Perspective provides an overview of strategies that use molecular enhancement of heterogeneous catalysts to improve activity, efficiency and selectivity in the further development of CO2RR.
Abstract: 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.
332 citations
TL;DR: In this article, a single-pass CO2 utilization of 77% was achieved with a conversion efficiency of 50% toward multicarbon products (ethylene, ethanol, and 1-propanol) at a current density of 1.2 amperes per square centimeter and a full cell voltage of 4.2 volts.
Abstract: Carbon dioxide electroreduction (CO2R) is being actively studied as a promising route to convert carbon emissions to valuable chemicals and fuels. However, the fraction of input CO2 that is productively reduced has typically been very low, <2% for multicarbon products; the balance reacts with hydroxide to form carbonate in both alkaline and neutral reactors. Acidic electrolytes would overcome this limitation, but hydrogen evolution has hitherto dominated under those conditions. We report that concentrating potassium cations in the vicinity of electrochemically active sites accelerates CO2 activation to enable efficient CO2R in acid. We achieve CO2R on copper at pH <1 with a single-pass CO2 utilization of 77%, including a conversion efficiency of 50% toward multicarbon products (ethylene, ethanol, and 1-propanol) at a current density of 1.2 amperes per square centimeter and a full-cell voltage of 4.2 volts.
325 citations
01 Mar 2019
TL;DR: In this paper, the authors discuss the current understanding of CO2 hydrogenation within these concepts, from fundamental mechanistic aspects to several parameters that will ultimately define its technical and economic feasibility on Earth and in space.
Abstract: The Sabatier reaction (that is, CO2 methanation) is undergoing a revival for two main reasons. First, the power-to-gas concept offers the prospect of large-scale recycling of (point source) CO2 emissions, in combination with the use of large quantities of renewable energy to form methane. When this can be achieved in a cost-effective manner, it can use the gas distribution infrastructure that already exists. However, methanation is no simple panacea to the detrimental environmental effect of CO2 emissions, and reaction products other than methane should also be targeted. Second, methanation has been identified as an important reaction to facilitate long-term space exploration missions by space agencies, such as NASA. This Perspective discusses the current understanding of CO2 hydrogenation within these concepts, from fundamental mechanistic aspects to several parameters that will ultimately define its technical and economic feasibility on Earth and in space, as we transition into the era of small-molecule activation.
322 citations
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TL;DR: In this paper, the formal relationship between US Vanderbilt-type pseudopotentials and Blochl's projector augmented wave (PAW) method is derived and the Hamilton operator, the forces, and the stress tensor are derived for this modified PAW functional.
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TL;DR: An improved way of estimating the local tangent in the nudged elastic band method for finding minimum energy paths is presented, and examples given where a complementary method, the dimer method, is used to efficiently converge to the saddle point.
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