Electrochemical Conversion of CO<sub>2</sub> and CH<sub>4</sub> at Subzero Temperatures

Sargeant, Elizabeth; Kolodziej, Adam; Duff, Cécile S. Le; Rodríguez, Paramaconi

doi:10.1021/acscatal.0c01676

Cited by 23 publications

(40 citation statements)

References 67 publications

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“…Improved catalysis by stabilization of unstable radicals in a suitable cage might be a general feature in catalysis, as suggested by recent reports involving aldehyde reduction 57 and reports of anti-Arrhenius kinetics in the electroreduction and electro-oxidation, respectively, of CO 2 and CH 4 in gas hydrates at sub-zero temperatures. 58 Our results are also consistent with very recent reports on the relevance of electrostatic stabilization of the CO 2 − radical for the electrochemical reduction of CO 2 . 2,59−61 This is also the first time that equilibrium potentials in nonaqueous solution have been calculated in the actual chemical environment and directly compared with experiments to reveal eventual catalytic effects of the solvent, excluding effects from other components.…”

Section: Discussionsupporting

confidence: 93%

“…Our studies confirm that the EBH mixture lowers the overpotential for CO 2 reduction by shifting the CO 2 /CO 2 – equilibrium potential positively, although the catalytic effect is not due to the formation of EMIM–CO 2 complexes and might instead be connected to stabilization through hydrogen bonding of the CO 2 – radical inside a water cage in a water-in-salt environment. Improved catalysis by stabilization of unstable radicals in a suitable cage might be a general feature in catalysis, as suggested by recent reports involving aldehyde reduction and reports of anti-Arrhenius kinetics in the electroreduction and electro-oxidation, respectively, of CO 2 and CH 4 in gas hydrates at sub-zero temperatures . Our results are also consistent with very recent reports on the relevance of electrostatic stabilization of the CO 2 – radical for the electrochemical reduction of CO 2 . ,− …”

Section: Discussionsupporting

confidence: 92%

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Water-In-Salt Environment Reduces the Overpotential for Reduction of CO₂ to CO₂^– in Ionic Liquid/Water Mixtures

et al. 2022

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We report a combined computational and experimental work aimed at estimating the equilibrium potential for the electroreduction of CO 2 to CO 2 − (widely accepted to be a crucial and overpotential-determining step) and at providing an alternative view on the reason behind the lower overpotential for CO 2 reduction in imidazolium-based ionic liquid/water mixtures. To begin with, we obtained an 80 ps ab-initio molecular dynamics trajectory of the CO 2 − solvation structures in an 18% EMIM−BF 4 / water mixture, which delivered no evidence of interaction between EMIM + and CO 2 − . Next, using the Fc + /Fc couple as the nonaqueous reference, we calculated the equilibrium potential of the CO 2 /CO 2 − couple in the mixture and aligned it with the aqueous SHE scale, proving that the equilibrium potential of CO 2 /CO 2 − in the mixture is about 0.3 V less negative than in the aqueous medium. We then looked for the origin of this catalytic effect by comparing the computed vibrational spectra with experimental Fourier transform infrared spectra. This revealed the presence of two water populations in the mixture, namely, bulk-like water and water in the vicinity of EMIM−BF 4 . Finally, we compared the hydrogen bonding interactions between the CO 2 − radical and H 2 O molecules in water and in the mixture, which showed that stabilization of CO 2 − by water molecules in the EMIM−BF 4 /water mixture is stronger than in the aqueous medium. This suggests that water in EMIM−BF 4 /water mixtures could be responsible for the low overpotential reported in these kinds of electrolytes.

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Section: Discussionsupporting

confidence: 93%

Section: Discussionsupporting

confidence: 92%

Water-In-Salt Environment Reduces the Overpotential for Reduction of CO₂ to CO₂^– in Ionic Liquid/Water Mixtures

et al. 2022

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“…The general pattern that could be recognized at both temperatures is that after the noble metals, that are the most active HER electrocatalysts, the second most active group are the triad of iron, then the coinage metals and at the end the sp‐metals, with unusual, almost inverse, temperature dependence of Co, Ag and Au. This could be due to anomalous temperature dependence of the Tafel slope (drop of Tafel's slope with temperature) [27–30] or due to phenomena of negative activation energy [31] also known as anti‐Arrhenius behavior [32] . Both phenomena are beyond the scope of this particular analysis, but they will be analyzed in future works.…”

Section: Resultsmentioning

confidence: 97%

“…This could be due to anomalous temperature dependence of the Tafel slope (drop of Tafel's slope with temperature) [27][28][29][30] or due to phenomena of negative activation energy [31] also known as anti-Arrhenius behavior. [32] Both phenomena are beyond the scope of this particular analysis, but they will be analyzed in future works.…”

Section: Her Activity Trends In Alkaline Mediamentioning

confidence: 99%

Electrocatalysis Beyond 2020: How to Tune the Preexponential Frequency Factor

et al. 2021

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After a century of research on electrocatalytic reactions, a universal theory of electrocatalysis is still not established due to limited understanding of complex energy conversion processes at electrified electrode‐electrolyte interfaces. Most of the research efforts directed toward the acceleration of important electrocatalytic reactions (e. g. hydrogen evolution reaction) were in the direction of minimizing activation energy by tuning the adsorption energies of key intermediates. This kind of approach is well‐established and, importantly, in some cases it was valuable by predicting the design of electrocatalysts with advanced properties. However, in some very important research endeavors, advancement in performance of newly designed electrocatalysts could not be attributed to altered/minimized activation energy. Important to note is that modern electrocatalysis almost completely disregards influence of the preexponential factor on reaction rate. In this work, we open some important questions relevant for future of electrocatalysis and electrochemical energy conversion, with special focus on preexponential factor as major contributor to electrocatalytic reaction rate.

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“…Intense research efforts have been focused on developing novel catalytic materials and understanding the influence of structural, 1−4 compositional, 5−13 and crystallographic properties 14,15 of metallic catalysts on the carbon dioxide reduction reaction (CO 2 RR). However, recent studies have shown that experimental parameters such as temperature, 16 partial pressure of CO 2 , 17 and other electrolyte conditions play critical roles in dictating both CO 2 RR selectivity and activity. For instance, trace metal impurity associated with bicarbonate and carbonate salts, 18,19 Ag/AgCl reference electrodes, 20 and even trace gaseous impurity 21 in reagent gas stream has been witnessed to dramatically steer the hydrogen evolution reaction (HER) and CO 2 RR selectivity.…”

Section: ■ Introductionmentioning

confidence: 99%

Surfactant Perturbation of Cation Interactions at the Electrode–Electrolyte Interface in Carbon Dioxide Reduction

et al. 2020

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Interfacial properties at the boundary between the electrode and electrolyte have important effects on the surface reactivity in electrocatalysis. Ionic additives and electrolyte ions can serve as promoters for specific reaction pathways. The judicious addition of these charged species thus represents a rich chemical strategy for tuning the electrode−electrolyte interface to achieve high product selectivity and catalytic activity. We have previously shown that trace amounts of surfactant can efficiently suppress the hydrogen evolution reaction (HER) and promote the carbon dioxide reduction (CO 2 RR) toward CO and HCOO − on a polycrystalline Cu foil working electrode. The major focus of herein study is to identify the impact of a model surfactant, cetyltrimethylammonium bromide (CTAB), on the double-layer structure in the presence of different alkali metal cations during electrocatalytic CO 2 RR. We postulated that the alkali cations and the positively charged surfactant headgroup will compete for a position at the negatively biased Cu electrode, leading to potentially synergistic effects on the catalytic performance. Indeed, it was observed that the positively charged trimethylammonium surfactant molecules effectively displace the alkali cations and suppress HER. However, the CO 2 RR activity and selectivity are nearly independent with respect to the identity of the alkali cations (Li + , Na + , and K + ) in the presence of CTAB. Cesium cations defy this trend, where high HCOO − activity is observed. A molecular model of the double layer is proposed where CTAB molecules are competing for a position at the outer Helmholtz plane (OHP), resulting in only a small concentration of electrolyte cation at the electrode surface in the presence of CTAB. Furthermore, we postulate that the decrease in C 2 H 4 activity is due to interfacial hydrophobicity caused by surfactant accumulation. We expect that these fundamental understandings will lead to advanced strategies for designing efficient organic additive to modulate the double-layer structure and optimize for selective smallmolecule activation.

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Electrochemical Conversion of CO₂ and CH₄ at Subzero Temperatures

Cited by 23 publications

References 67 publications

Water-In-Salt Environment Reduces the Overpotential for Reduction of CO₂ to CO₂^– in Ionic Liquid/Water Mixtures

Water-In-Salt Environment Reduces the Overpotential for Reduction of CO₂ to CO₂^– in Ionic Liquid/Water Mixtures

Electrocatalysis Beyond 2020: How to Tune the Preexponential Frequency Factor

Surfactant Perturbation of Cation Interactions at the Electrode–Electrolyte Interface in Carbon Dioxide Reduction

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Electrochemical Conversion of CO2 and CH4 at Subzero Temperatures

Cited by 23 publications

References 67 publications

Water-In-Salt Environment Reduces the Overpotential for Reduction of CO2 to CO2– in Ionic Liquid/Water Mixtures

Water-In-Salt Environment Reduces the Overpotential for Reduction of CO2 to CO2– in Ionic Liquid/Water Mixtures

Electrocatalysis Beyond 2020: How to Tune the Preexponential Frequency Factor

Surfactant Perturbation of Cation Interactions at the Electrode–Electrolyte Interface in Carbon Dioxide Reduction

Contact Info

Product

Resources

About

Electrochemical Conversion of CO₂ and CH₄ at Subzero Temperatures

Water-In-Salt Environment Reduces the Overpotential for Reduction of CO₂ to CO₂^– in Ionic Liquid/Water Mixtures

Water-In-Salt Environment Reduces the Overpotential for Reduction of CO₂ to CO₂^– in Ionic Liquid/Water Mixtures