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 , the authors demonstrate CO2 electroreduction in strongly acidic electrolyte (pH ≤ 1) on electrochemically reduced porous Cu nanosheets by combining the confinement effect and cation effect to synergistically modulate the local microenvironment.
Abstract: Electrochemical CO2 reduction to multicarbon products faces challenges of unsatisfactory selectivity, productivity, and long-term stability. Herein, we demonstrate CO2 electroreduction in strongly acidic electrolyte (pH ≤ 1) on electrochemically reduced porous Cu nanosheets by combining the confinement effect and cation effect to synergistically modulate the local microenvironment. A Faradaic efficiency of 83.7 ± 1.4% and partial current density of 0.56 ± 0.02 A cm-2, single-pass carbon efficiency of 54.4%, and stable electrolysis of 30 h in a flow cell are demonstrated for multicarbon products in a strongly acidic aqueous electrolyte consisting of sulfuric acid and KCl with pH ≤ 1. Mechanistically, the accumulated species (e.g., K+ and OH-) on the Helmholtz plane account for the selectivity and activity toward multicarbon products by kinetically reducing the proton coverage and thermodynamically favoring the CO2 conversion. We find that the K+ cations facilitate C-C coupling through local interaction between K+ and the key intermediate *OCCO.
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12 Feb 2021
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TL;DR: In this article , the authors investigated the role of dynamic active site generation and the representative contribution of OVSM pathway for efficient OER performance and confirmed mechanism switch to oxygen-vacancy-site mechanism (OVSM) pathway on lattice oxygen.
Abstract: The regulation of atomic and electronic structures of active sites plays an important role in the rational design of oxygen evolution reaction (OER) catalysts toward electrocatalytic hydrogen generation. However, the precise identification of the active sites for surface reconstruction behavior during OER remains elusive for water‐alkali electrolysis. Herein, irreversible reconstruction behavior accompanied by copper dynamic evolution for cobalt iron layered double hydroxide (CoFe LDH) precatalyst to form CoFeCuOOH active species with high‐valent Co species is reported, identifying the origin of reconstructed active sites through operando UV‐Visible (UV–vis), in situ Raman, and X‐ray absorption fine‐structure (XAFS) spectroscopies. Density functional theory analysis rationalizes this typical electronic structure evolution causing the transfer of intramolecular electrons to form ligand holes, promoting the reconstruction of active sites. Specifically, unambiguous identification of active sites for CoFeCuOOH is explored by in situ 18O isotope‐labeling differential electrochemical mass spectrometry (DEMS) and supported by theoretical calculation, confirming mechanism switch to oxygen‐vacancy‐site mechanism (OVSM) pathway on lattice oxygen. This work enables to elucidate the vital role of dynamic active‐site generation and the representative contribution of OVSM pathway for efficient OER performance.
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TL;DR: In this article, the authors steer CO2 electroreduction toward methane (CH4) or ethylene (C2H4) production by controlling the loading of copper phosphate (Cu3(PO4)2) nanosheets on electrode.
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TL;DR: In this article, a Pt-nano-sensor is positioned in the vicinity of the working gas diffusion electrode (GDE), allowing to monitor changes invoked by reactions proceeding within an otherwise inaccessible porous GDE by potentiodynamic measurements at the Pt-tip nanosensor.
Abstract: Discerning the influence of electrochemical reactions on the electrode microenvironment is an unavoidable topic for electro-chemical reactions that involve the production of OH - and the con-sumption of water. That is particularly true for the carbon dioxide re-duction reaction (CO 2 RR) which together with the competing hydro-gen evolution reaction exert changes in the local OH - and H 2 O activi-ty which in turn can possibly affect activity, stability and selectivity of the CO 2 RR. We determine the local OH - and H 2 O activity in close proximity to a CO 2 converting Ag-based gas diffusion electrode (GDE) with product analysis using gas chromatography. A Pt-nano-sensor is positioned in the vicinity of the working GDE using shear-force-based scanning electrochemical microscopy (SECM) approach curves allowing to monitor changes invoked by reactions proceeding within an otherwise inaccessible porous GDE by potentiodynamic measurements at the Pt-tip nanosensor. We show that high turnover HER/CO 2 RR at a GDE lead to modulations of the alkalinity of the local electrolyte, that resemble a 16 M KOH solution, variations which are in turn linked to the reaction selectivity.
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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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