skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Electrokinetic and in situ spectroscopic investigations of CO electrochemical reduction on copper
Abstract Rigorous electrokinetic results are key to understanding the reaction mechanisms in the electrochemical CO reduction reaction (CORR), however, most reported results are compromised by the CO mass transport limitation. In this work, we determined mass transport-free CORR kinetics by employing a gas-diffusion type electrode and identified dependence of catalyst surface speciation on the electrolyte pH using in-situ surface enhanced vibrational spectroscopies. Based on the measured Tafel slopes and reaction orders, we demonstrate that the formation rates of C 2+ products are most likely limited by the dimerization of CO adsorbate. CH 4 production is limited by the CO hydrogenation step via a proton coupled electron transfer and a chemical hydrogenation step of CO by adsorbed hydrogen atom in weakly (7 < pH < 11) and strongly (pH > 11) alkaline electrolytes, respectively. Further, CH 4 and C 2+ products are likely formed on distinct types of active sites.  more » « less
Award ID(s):
1651625
PAR ID:
10331972
Author(s) / Creator(s):
; ; ; ; ; ;
Date Published:
Journal Name:
Nature Communications
Volume:
12
Issue:
1
ISSN:
2041-1723
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; (, Beilstein Journal of Organic Chemistry)
    Two routes to the title compounds are evaluated. First, a ca. 0.01 M CH 2 Cl 2 solution of H 3 B·P((CH 2 ) 6 CH=CH 2 ) 3 ( 1 ·BH 3 ) is treated with 5 mol % of Grubbs' first generation catalyst (0 °C to reflux), followed by H 2 (5 bar) and Wilkinson's catalyst (55 °C). Column chromatography affords H 3 B·P( n- C 8 H 17 ) 3 (1%), H 3 B· P ((CH 2 ) 13 C H 2 )( n -C 8 H 17 ) (8%; see text for tie bars that indicate additional phosphorus–carbon linkages, which are coded in the abstract with italics), H 3 B· P ((CH 2 ) 13 C H 2 )((CH 2 ) 14 ) P ((CH 2 ) 13 C H 2 )·BH 3 ( 6 ·2BH 3 , 10%), in,out -H 3 B·P((CH 2 ) 14 ) 3 P·BH 3 ( in,out - 2 ·2BH 3 , 4%) and the stereoisomer ( in,in / out,out )- 2 ·2BH 3 (2%). Four of these structures are verified by independent syntheses. Second, 1,14-tetradecanedioic acid is converted (reduction, bromination, Arbuzov reaction, LiAlH 4 ) to H 2 P((CH 2 ) 14 )PH 2 ( 10 ; 76% overall yield). The reaction with H 3 B·SMe 2 gives 10 ·2BH 3 , which is treated with n -BuLi (4.4 equiv) and Br(CH 2 ) 6 CH=CH 2 (4.0 equiv) to afford the tetraalkenyl precursor (H 2 C=CH(CH 2 ) 6 ) 2 (H 3 B)P((CH 2 ) 14 )P(BH 3 )((CH 2 ) 6 CH=CH 2 ) 2 ( 11 ·2BH 3 ; 18%). Alternative approaches to 11 ·2BH 3 (e.g., via 11 ) were unsuccessful. An analogous metathesis/hydrogenation/chromatography sequence with 11 ·2BH 3 (0.0010 M in CH 2 Cl 2 ) gives 6 ·2BH 3 (5%), in,out - 2 ·2BH 3 (6%), and ( in,in / out,out )- 2 ·2BH 3 (7%). Despite the doubled yield of 2 ·2BH 3 , the longer synthesis of 11 ·2BH 3 vs 1 ·BH 3 renders the two routes a toss-up; neither compares favorably with precious metal templated syntheses. 
    more » « less
  2. ; ; ; ; ; ; (, Energy & Environmental Science)
    Nanostructured Cu catalysts have increased the selectivities and geometric activities for high value C–C coupled (C 2 ) products (ethylene, ethanol, and acetate) in the electrochemical CO (2) reduction reaction (CO (2) RR). The selectivity among the high-value C 2 products is also altered, where for instance the yield of acetate increases with alkalinity and is dependent on the catalyst morphology. The reaction mechanisms behind the selectivity towards acetate vs. other C 2 products remain controversial. In this work, we elucidate the reaction mechanism for acetate formation by using ab initio simulations, a coupled kinetic-transport model, and loading dependent experiments. We find that trends in acetate selectivity can be rationalized from variations in electrolyte pH and the local mass transport properties of the catalyst and not from changes in Cu's intrinsic activity. The selectivity mechanism originates from the transport of ketene, a stable (closed shell) intermediate, away from the catalyst surface into solution where it reacts to form acetate. While this type of mechanism has not yet been discussed in the CO (2) RR, variants of it may explain similar selectivity fluctuations observed for other stable intermediates like CO and acetaldehyde. Our proposed mechanism suggests that acetate selectivity increases with increasing pH, decreasing catalyst roughness and significantly varies with the applied potential. 
    more » « less
  3. ; ; ; ; ; ; ; ; (, ENERGY & ENVIRONMENTAL MATERIALS)
    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
  4. ; ; ; ; ; (, Journal of Physics D: Applied Physics)
    Abstract In this work, we investigated atmospheric pressure plasma jet (APPJ)-assisted methane oxidation over a Ni-SiO 2 /Al 2 O 3 catalyst. We evaluated possible reaction mechanisms by analyzing the correlation of gas phase, surface and plasma-produced species. Plasma feed gas compositions, plasma powers, and catalyst temperatures were varied to expand the experimental parameters. Real-time Fourier-transform infrared spectroscopy was applied to quantify gas phase species from the reactions. The reactive incident fluxes generated by plasma were measured by molecular beam mass spectroscopy using an identical APPJ operating at the same conditions. A strong correlation of the quantified fluxes of plasma-produced atomic oxygen with that of CH 4 consumption, and CO and CO 2 formation implies that O atoms play an essential role in CH 4 oxidation for the investigated conditions. With the integration of APPJ, the apparent activation energy was lowered and a synergistic effect of 30% was observed. We also performed in-situ diffuse reflectance infrared Fourier-transform spectroscopy to analyze the catalyst surface. The surface analysis showed that surface CO abundance mirrored the surface coverage of CH n at 25 °C. This suggests that CH n adsorbed on the catalyst surface as an intermediate species that was subsequently transformed into surface CO. We observed very little surface CH n absorbance at 500 °C, while a ten-fold increase of surface CO and stronger CO 2 absorption were seen. This indicates that for a nickel catalyst at 500 °C, the dissociation of CH 4 to CH n may be the rate-determining step in the plasma-assisted CH 4 oxidation for our conditions. We also found the CO vibrational frequency changes from 2143 cm −1 for gas phase CO to 2196 cm −1 for CO on a 25 °C catalyst surface, whereas the frequency of CO on a 500 °C catalyst was 2188 cm −1 . The change in CO vibrational frequency may be related to the oxidation of the catalyst. 
    more » « less
  5. ; ; ; (, Journal of Materials Chemistry A)
    In this report, CeO 2 and SiO 2 supported 1 wt% Ru catalysts were synthesized and studied for dry reforming of methane (DRM) by introducing non-thermal plasma (NTP) in a dielectric barrier discharge (DBD) fixed bed reactor. From quadrupole mass spectrometer (QMS) data, it is found that introducing non-thermal plasma in thermo-catalytic DRM promotes higher CH 4 and CO 2 conversion and syngas (CO + H 2 ) yield than those under thermal catalysis only conditions. According to the H 2 -TPR, CO 2 -TPD, and CO-TPD profiles, reducible CeO 2 supported Ru catalysts presented better activity compared to their irreducible SiO 2 supported Ru counterparts. For instance, the molar concentrations of CO and H 2 were 16% and 9%, respectively, for plasma-assisted thermo-catalytic DRM at 350 °C, while no apparent conversion was observed at the same temperature for thermo-catalytic DRM. Highly energetic electrons, ions, and radicals under non-equilibrium and non-thermal plasma conditions are considered to contribute to the activation of strong C–H bonds in CH 4 and C–O bonds in CO 2 , which significantly improves the CH 4 /CO 2 conversion during DRM reaction at low temperatures. At 450 °C, the 1 wt% Ru/CeO 2 nanorods sample showed the highest catalytic activity with 51% CH 4 and 37% CO 2 conversion compared to 1 wt% Ru/CeO 2 nanocubes (40% CH 4 and 30% CO 2 ). These results clearly indicate that the support shape and reducibility affect the plasma-assisted DRM reaction. This enhanced DRM activity is ascribed to the surface chemistry and defect structures of the CeO 2 nanorods support that can provide active surface facets, higher amounts of mobile oxygen and oxygen vacancy, and other surface defects. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email