An official website of the United States government
Regulating the selectivity toward a target hydrocarbon product is still the focus of CO2electroreduction. Here, we discover that the original surface Cu species in Cu gas‐diffusion electrodes plays a more important role than the surface roughness, local pH, and facet in governing the selectivity toward C1or C2hydrocarbons. The selectivity toward C2H4progressively increases, while CH4decreases steadily upon lowering the Cu oxidation species fraction. At a relatively low electrodeposition voltage of 1.5 V, the Cu gas‐diffusion electrode with the highest Cuδ+/Cu0ratio favors the pathways of hydrogenation to form CH4with maximum Faradaic efficiency of 65.4% and partial current density of 228 mA cm−2at −0.83 V vs RHE. At 2.0 V, the Cu gas‐diffusion electrode with the lowest Cuδ+/Cu0ratio prefers C–C coupling to form C2+products with Faradaic efficiency topping 80.1% at −0.75 V vs RHE, where the Faradaic efficiency of C2H4accounts for 46.4% and the partial current density of C2H4achieves 279 mA cm−2. This work demonstrates that the selectivity from CH4to C2H4is switchable by tuning surface Cu species composition of Cu gas‐diffusion electrodes.
more »
« less
Effect of Electrolyte Composition and Concentration on Pulsed Potential Electrochemical CO 2 Reduction
Abstract With rising CO2emissions and growing interests towards CO2valorization, electrochemical CO2reduction (eCO2R) has emerged as a promising prospect for carbon recycling and chemical energy storage. Yet, product selectivity and electrocatalyst longevity persist as obstacles to the broad implementation of eCO2R. A possible solution to ameliorate this challenge is to pulse the applied potential. However, it is currently unclear whether and how the trends and lessons obtained from the more conventional constant potential eCO2R translate to pulsed potential eCO2R. In this work, we report that the relationship between electrolyte concentration/composition and product distribution for pulsed potential eCO2R is different from constant potential eCO2R. In the case of constant potential eCO2R, increasing KHCO3concentration favors the formation of H2and CH4. In contrast, for pulsed potential eCO2R, H2formation is suppressed due to the periodic desorption of surface protons, while CH4is still favored. In the case of KCl, increasing the concentration during constant potential eCO2R does not affect product distribution, mainly producing H2and CO. However, increasing KCl concentration during pulsed potential eCO2R persistently suppresses H2formation and greatly favors C2products, reaching 71 % Faradaic efficiency. Collectively, these results provide new mechanistic insights into the pulsed eCO2R mechanism within the context of proton‐donator ability and ionic conductivity.
more »
« less
- Award ID(s):
- 1805400
- PAR ID:
- 10236329
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ChemElectroChem
- Volume:
- 8
- Issue:
- 4
- ISSN:
- 2196-0216
- Format(s):
- Medium: X Size: p. 681-688
- Size(s):
- p. 681-688
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Tidal wetlands provide valuable ecosystem services, including storing large amounts of carbon. However, the net exchanges of carbon dioxide (CO2) and methane (CH4) in tidal wetlands are highly uncertain. While several biogeochemical models can operate in tidal wetlands, they have yet to be parameterized and validated against high‐frequency, ecosystem‐scale CO2and CH4flux measurements across diverse sites. We paired the Cohort Marsh Equilibrium Model (CMEM) with a version of the PEPRMT model called PEPRMT‐Tidal, which considers the effects of water table height, sulfate, and nitrate availability on CO2and CH4emissions. Using a model‐data fusion approach, we parameterized the model with three sites and validated it with two independent sites, with representation from the three marine coasts of North America. Gross primary productivity (GPP) and ecosystem respiration (Reco) modules explained, on average, 73% of the variation in CO2exchange with low model error (normalized root mean square error (nRMSE) <1). The CH4module also explained the majority of variance in CH4emissions in validation sites (R2 = 0.54; nRMSE = 1.15). The PEPRMT‐Tidal‐CMEM model coupling is a key advance toward constraining estimates of greenhouse gas emissions across diverse North American tidal wetlands. Further analyses of model error and case studies during changing salinity conditions guide future modeling efforts regarding four main processes: (a) the influence of salinity and nitrate on GPP, (b) the influence of laterally transported dissolved inorganic C on Reco, (c) heterogeneous sulfate availability and methylotrophic methanogenesis impacts on surface CH4emissions, and (d) CH4responses to non‐periodic changes in salinity.more » « less
-
Abstract Converting CO2into industrially useful products is an appealing strategy for utilization of an abundant chemical resource. Electrochemical CO2reduction (eCO2R) offers a pathway to convert CO2into CO and ethylene, using renewable electricity. These products can be efficiently copolymerized by organometallic catalysts to generate polyketones. However, the conditions for these reactions are very different, presenting the challenge of coupling microenvironments typically encountered for the transformation of CO2into highly complex but desirable multicarbon products. Herein, we present a system to produce polyketone plastics entirely derived from CO2and water, where both the CO and C2H4intermediates are produced by eCO2R. In this system, a combination of Cu and Ag gas diffusion electrodes is used to generate a gas mixture with nearly equal concentrations of CO and C2H4, and a recirculatory CO2reduction loop is used to reach concentrations of above 11% each, leading to a current‐to‐polymer efficiency of up to 51% and CO2utilization of 14%.more » « less
-
Abstract The dialkyl malonate derived 1,3‐diphosphines R2C(CH2PPh2)2(R=a, Me;b, Et;c,n‐Bu;d,n‐Dec;e, Bn;f,p‐tolCH2) are combined with (p‐tol3P)2PtCl2ortrans‐(p‐tol3P)2Pt((C≡C)2H)2to give the chelatescis‐(R2C(CH2PPh2)2)PtCl2(2 a–f, 94–69 %) orcis‐(R2C(CH2PPh2)2)Pt((C≡C)2H)2(3 a–f, 97–54 %). Complexes3 a–dare also available from2 a–dand excess 1,3‐butadiyne in the presence of CuI (cat.) and excess HNEt2(87–65 %). Under similar conditions,2and3react to give the title compounds [(R2C(CH2PPh2)2)[Pt(C≡C)2]4(4 a–f; 89–14 % (64 % avg)), from which ammonium salts such as the co‐product [H2NEt2]+Cl−are challenging to remove. Crystal structures of4 a,bshow skew rhombus as opposed to square Pt4geometries. The NMR and IR properties of4 a–fare similar to those of mono‐ or diplatinum model compounds. However, cyclic voltammetry gives only irreversible oxidations. As compared to mono‐platinum or Pt(C≡C)2Pt species, the UV‐visible spectra show much more intense and red‐shifted bands. Time dependent DFT calculations define the transitions and principal orbitals involved. Electrostatic potential surface maps reveal strongly negative Pt4C16cores that likely facilitate ammonium cation binding. Analogous electronic properties of Pt3C12and Pt5C20homologs and selected equilibria are explored computationally.more » « less
-
Abstract Oxygen-containing complex organic molecules are key precursors to biorelevant compounds fundamental for the origins of life. However, the untangling of their interstellar formation mechanisms has just scratched the surface, especially for oxygen-containing cyclic molecules. Here, we present the first laboratory simulation experiments featuring the formation of all three C2H4O isomers—ethylene oxide (c–C2H4O), acetaldehyde (CH3CHO), and vinyl alcohol (CH2CHOH)—in low-temperature model interstellar ices composed of carbon monoxide (CO) and ethanol (C2H5OH). Ice mixtures were exposed to galactic cosmic-ray proxies with an irradiation dose equivalent to a cold molecular cloud aged (7 ± 2) × 105yr. These biorelevant species were detected in the gas phase through isomer-selective photoionization reflectron time-of-flight mass spectrometry during temperature-programmed desorption. Isotopic labeling experiments reveal that ethylene oxide is produced from ethanol alone, providing the first experimental evidence to support the hypothesis that ethanol serves as a precursor to the prototype epoxide in interstellar ices. These findings reveal feasible pathways for the formation of all three C2H4O isomers in ethanol-rich interstellar ices, offering valuable constraints on astrochemical models for their formation. Our results suggest that ethanol is a critical precursor to C2H4O isomers in interstellar environments, representing a critical step toward unraveling the formation mechanisms of oxygen-containing cyclic molecules, aldehydes, and their enol tautomers from alcohols in interstellar ices.more » « less
