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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TL;DR: In this paper , a single-layered porous aza-fused π-conjugated graphene-analogous 2D materials (PAG) with well-organized nanopores and consistently allocated nitrogen atoms as supporting specie to coordinate cobalt (Co) atom through nitrogen inside (Co-PAG), for CO 2 conversion to formic-acid by hydrogenation and electrochemical approaches.
Abstract: • Single-layered porous aza-fused π-conjugated graphene analogous 2D materials (PAG) with a distinct crystalline carbonic framework, highly ordered specific pores, and consistently dispersed nitrogen atoms are stable and active support to coordinate Co. • The spin density around the active site is increased with cobalt coordination resulting in good catalytic activity around Co sites. The band gap of Co-PAG is reduced to 0.7 eV compare to PAG which is 1.79 eV. Moreover, both PAG and Co-PAG show outstanding thermal stability even at 1000 K. • By hydrogenation and electroreduction approaches we find that PAG and Co-PAG materials are active and stable catalyst for CO 2 conversion to formic acid • The highest barrier along the complete reaction path is about 0.78 eV which is feasible for the experiment to carry out this reaction at an elevated temperature. • The overpotential requires for PAG material in CO 2 RR to formic-acid is 0.46 V vs. RHE which is significantly larger than for Co-PAG (0.18 V), which suggests that Co-doping in PAG material makes the formic-acid reaction path significantly energy favorable. In this work, we report novel single-layered porous aza-fused π-conjugated graphene-analogous 2D materials (PAG) with well-organized nanopores and consistently allocated nitrogen atoms as supporting specie to coordinate cobalt (Co) atom through nitrogen inside (Co-PAG), for CO 2 conversion to formic-acid by hydrogenation and electrochemical approaches. Because of the synergetic effect of structural characteristics and Co-coordination, the band gap of Co-PAG is reduced to 0.7 eV, while that of PAG is 1.79 eV. The molecular dynamic (MD) simulations uncover the stability of PAG/Co-PAG. From reaction pathway analysis, it is concluded that Co-PAG can effectively hydrogenate CO 2 to formic acid. The highest barrier is 0.78 eV, which is feasible for experiments to carry out this reaction at elevated temperatures. Furthermore, the overpotential requirement for PAG material in CO 2 electroreduction (CO 2 RR) to formic-acid is 0.46 V which is significantly larger than that for Co-PAG (0.18 V). Both PAG and Co-PAG surfaces retain higher selectivity for formic acid than that of carbon mono oxides and hydrogen evolution reaction (HER), and cobalt coordination in PAG support makes the formic-acid reaction path significantly energy favorable. These results confirm that PAG can be possible catalyst support and that Co-coordination in PAG material makes the formic-acid reaction path significantly more energy favorable. Cobalt coordinated single-layered porous aza-fused π-conjugated graphene analogous 2D material a stable and active electrocatalyst for CO 2 reduction reaction
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TL;DR: In this article, a review of the electrolyzer configurations and operating principles of widely used electrolyzers and summarized advantages and disadvantages of each of them for carbon dioxide reduction reaction (CO2RR) is presented.
Abstract: The electrocatalytic carbon dioxide reduction reaction (CO2RR) provides a way to use CO2 to produce valuable fuels and feedstocks powered by renewable electricity. Considerable efforts have been put into the development of catalysts with the aim to achieve high CO2RR performance, i.e., high activity, high product selectivity, and low overpotentials. However, few reports have been focused on the studies of electrolyzers, which are the key component toward the implementation of CO2RR on commercial scales. In this review, we overview the configurations and operating principles of widely used electrolyzers and summarize advantages and disadvantages of each. We discuss in detail recent progress of the membrane electrode assembly (MEA) electrolyzer, which is believed to be promising for commercialization of the CO2RR. Finally, we look at challenges and suggest strategies for future development of MEA electrolyzers.
25 citations
TL;DR: In this article , the current performance status and challenges are discussed and effective strategies are outlined to promote C2+ evolution and further, the correlation between the composition, structure, and morphology of carbon catalysts and their catalytic behavior is elucidated to establish catalytic mechanisms and critical factors determining C 2+ performance.
Abstract: Electrochemical CO2 reduction offers a compelling route to mitigate atmospheric CO2 concentration and store intermittent renewable energy in chemical bonds. Beyond C1, C2+ feedstocks are more desirable due to their higher energy density and more significant market need. However, the CO2‐to‐C2+ reduction suffers from significant barriers of CC coupling and complex reaction pathways. Due to remarkable tunability over morphology/pore architecture along with great feasibility of functionalization to modify the electronic and geometric structures, carbon materials, serving as active components, supports, and promoters, provide exciting opportunities to tune both the adsorption properties of intermediates and the local reaction environment for the CO2 reduction, offering effective solutions to enable CC coupling and steer C2+ evolution. However, general design principles remain ambiguous, causing an impediment to rational catalyst refinement and application thrusts. This review clarifies insightful design principles for advancing carbon materials. First, the current performance status and challenges are discussed and effective strategies are outlined to promote C2+ evolution. Further, the correlation between the composition, structure, and morphology of carbon catalysts and their catalytic behavior is elucidated to establish catalytic mechanisms and critical factors determining C2+ performance. Finally, future research directions and strategies are envisioned to inspire revolutionary advancements.
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TL;DR: In this paper, the Bi2O3 nanosheets (NSs) with inherent hydrophobicity achieved a peak formate current density of 102.1 mA cm-2 and high formate Faradaic efficiency of >93% over a very wide potential window of 1000 mV.
Abstract: The ever-increasing concern for adverse climate changes has propelled worldwide research on the reduction of CO2 emission. In this regard, CO2 electroreduction (CER) to formate is one of the promising approaches to converting CO2 to a useful product. However, to achieve a high production rate of formate, the existing catalysts for CER fall short of expectation in maintaining the high formate selectivity and activity over a wide potential window. Through this study, we report that Bi2O3 nanosheets (NSs) grown on carbon nanofiber (CNF) with inherent hydrophobicity achieve a peak formate current density of 102.1 mA cm-2 and high formate Faradaic efficiency of >93% over a very wide potential window of 1000 mV. To the best of our knowledge, this outperforms all the relevant achievements reported so far. In addition, the Bi2O3 NSs on CNF demonstrate a good antiflooding capability when operating in a flow cell system and can deliver a current density of 300 mA cm-2. Molecular dynamics simulations indicate that the hydrophobic carbon surface can repel water molecules to form a robust solid-liquid-gas triple-phase boundary and a concentrated CO2 layer; both can boost CER activity with the local high concentration of CO2 and through inhibiting the hydrogen evolution reaction (HER) by reducing proton contacts. This water-repelling effect also increases the local pH at the catalyst surface, thus inhibiting HER further. More significantly, the concept and methodology of this hydrophobic engineering could be broadly applicable to other formate-producing materials from CER.
25 citations
TL;DR: In this article , hollow mesoporous carbon spheres (HMCS) are used to confine and protect Cu clusters to achieve high C2 selectivity, while the nanocavities formed by HMCS can effectively confine the in situ formed *CHO carbon intermediates, which facilitates the C-C bond coupling.
Abstract: Copper-based catalysts are widely used to adjust the activity and selectivity of CO2 electroreduction reactions (CO2RR). In this article, we choose to use hollow mesoporous carbon spheres (HMCS) to confine and protect Cu clusters to achieve high C2 selectivity. The electrocatalytic results show that when the amount of Cu clusters confined by HMCS reaches 20% (Cu/HMCS5-20%), the selectivity of C2 products reach 88.7% at − 1.0 V vs. RHE. In situ Fourier transform infrared spectroscopy (FTIRS) shows that Cu clusters confined and protected by HMCS is beneficial to the conversion of *CO to *CHO, while the nanocavities formed by HMCS can effectively confine the in situ formed *CHO carbon intermediates, which facilitates the C-C bond coupling to form C2H4 and C2H5OH. We proposes a method to improve the C2 selectivity of CO2RR and reduce the amount of Cu in CO2RR by using the confinement effect of HMCS.
25 citations
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