Mechanism of the electrochemical reduction of carbon dioxide at inert electrodes in media of low proton availability

Gennaro, Armando; Isse, Abdirisak Ahmed; Severin, Maria Gabriella; Vianello, E.; Bhugun, Iqbal; Savéant, Jean‐Michel

doi:10.1039/ft9969203963

Cited by 197 publications

(231 citation statements)

References 28 publications

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“…The resulting correlation is shown in Figure 8; interestingly, the points lie close to a 2 e − /CO 2 linear slope, whereas the often assumed reduction of CO 2 to carbonate and CO (acc. to: 2 CO 2 + 2 e -→ CO 3 2− + CO) [47][48][49] as well as the reduction of CO 2 to oxalate (acc. to: 2 CO 2 + 2 e -→ C 2 O 4 −2 ) 49-51 both would correspond to 1 e − /CO 2 .…”

Section: Resultsmentioning

confidence: 99%

Lithium Oxalate as Capacity and Cycle-Life Enhancer in LNMO/Graphite and LNMO/SiG Full Cells

Solchenbach

Wetjen

Pritzl

et al. 2018

J. Electrochem. Soc.

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In the present study, we explore the use of lithium oxalate as a "sacrificial salt" in combination with lithium nickel manganese spinel (LNMO) cathodes. By online electrochemical mass spectrometry (OEMS), we demonstrate that the oxidation of lithium oxalate to CO 2 (corresponding to 525 mAh/g) occurs quantitatively around 4.7 V vs. Li/Li + . LNMO/graphite cells containing 2.5 or 5 wt% lithium oxalate show an up to ∼11% higher initial discharge capacity and less capacity fade over 300 cycles (12% and 8% vs. 19%) compared to cells without lithium oxalate. In LNMO/SiG full-cells with an FEC-containing electrolyte solution, lithium oxalate leads to a better capacity retention (45% vs 20% after 250 cycles) and a higher coulombic efficiency throughout cycling (∼1%) compared to cells without lithium oxalate. When CO 2 from lithium oxalate oxidation is removed after formation, a similar capacity fading as in LNMO/SiG cells without lithium oxalate is observed. Hence, we attribute the improved cycling performance to the presence of CO 2 in the cells. Further analysis (e.g., FEC consumption by 19 F-NMR) indicate that CO 2 is an effective SEI-forming additive for SiG anodes, and that a combination of FEC and CO 2 has a synergistic effect on the lifetime of full-cells with SiG anodes. Lithium nickel manganese spinel (LiNi 0.5 Mn 1.5 O 4 , LNMO) is a promising cathode material for high energy lithium ion batteries due to its high operating potential around 4.7 V vs. Li/Li + , its high rate capability, structural stability and the absence of cobalt. However, its lower specific capacity (146 mAh/g LNMO ) compared to layered oxide materials (e.g. lithium nickel manganese cobalt oxide (NMC), specific capacity 150-250 mAh/g NMC ) 1 is regarded as a major drawback. In full-cells, the practically achievable capacity of LNMO is even lower, as the formation of the solid-electrolyte interphase (SEI) on the graphite anode consumes active lithium. For many layered oxide cathodes, however, the first cycle irreversible capacity of the cathode is similar to the capacity needed for SEI formation (∼20 mAh/g NMC ), and hence the practical discharge capacity of the cathode and the remaining active lithium are more or less balanced again. 2,3 In contrast, the first cycle irreversible capacity of LNMO (∼6 mAh/g LNMO ) is much lower than the capacity needed for SEI formation. This leads to a mismatch between active lithium and practical cathode capacity, i.e., there is not enough active lithium available to fully discharge the LNMO cathode during subsequent cycling.In cells with silicon-based anodes, active lithium losses on the anode are even higher compared to graphite, as the expansion of the silicon particles during the first lithiation leads to a continuous exposure of fresh, unpassivated silicon surface. 4 On this new surface, electrolyte reduction occurs instantaneously, which reduces the total lithium reservoir in the cell. Therefore, different ideas to increase the amount of active lithium in lithium ion full-cells have been suggested, ...

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Section: Resultsmentioning

confidence: 99%

Lithium Oxalate as Capacity and Cycle-Life Enhancer in LNMO/Graphite and LNMO/SiG Full Cells

Solchenbach

Wetjen

Pritzl

et al. 2018

J. Electrochem. Soc.

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“…The Tafel slope is given by the partial derivative of the overpotential η with respect to the logarithm of current,(30) which we apply to eq 4, yielding (5) Hence, the theoretical Tafel slope of 59 mV/decade for the proposed mechanism is consistent with our experimental measurement of a 60 ± 4.2 mV/decade ( Figure 5A). The preceding analysis involving the Tafel slope and orderdependence on p CO2 has also allowed us to exclude several alternative mechanisms, such as the self-coupling of two CO In studies done on mercury and lead in dimethylformamide, (38,(42)(43)(44)) the CO 2 -CO 2 -• adduct 3 is believed to reductively disproportionate to yield both CO 3 2-and CO, which is a terminal product on these electrodes. Our experimental observation of CO as a minor product on n-Cu/C electrodes ( Figure S4) is consistent with its appearance as an intermediate in our proposed mechanism.…”

Section: Continuum From Nanoparticle-like To Foil-like Behaviormentioning

confidence: 99%

Enhanced Electrochemical Methanation of Carbon Dioxide with a Dispersible Nanoscale Copper Catalyst

2014

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Although the vast majority of hydrocarbon fuels and products are presently derived from petroleum, there is much interest in the development of routes for synthesizing these same products by hydrogenating CO 2 . The simplest hydrocarbon target is methane, which can utilize existing infrastructure for natural gas storage, distribution, and consumption. Electrochemical methods for methanizing CO 2 currently suffer from a combination of low activities and poor selectivities. We demonstrate that copper nanoparticles supported on glassy carbon (n-Cu/C) achieve up to 4 times greater methanation current densities compared to high-purity copper foil electrodes. The n-Cu/ C electrocatalyst also exhibits an average Faradaic efficiency for methanation of 80% during extended electrolysis, the highest Faradaic efficiency for room-temperature methanation reported to date. We find that the level of copper catalyst loading on the glassy carbon support has an enormous impact on the morphology of the copper under catalytic conditions and the resulting Faradaic efficiency for methane. The improved activity and Faradaic efficiency for methanation involves a mechanism that is distinct from what is generally thought to occur on copper foils. Electrochemical data indicate that the early steps of methanation on n-Cu/C involve a pre-equilibrium one-electron transfer to CO 2 to form an adsorbed radical, followed by a rate-limiting nonelectrochemical step in which the adsorbed CO 2 radical reacts with a second CO 2 molecule from solution. These nanoscale copper electrocatalysts represent a first step toward the preparation of practical methanation catalysts that can be incorporated into membrane-electrode assemblies in electrolyzers.

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“…13,14 They observed a marked difference in the product distribution between direct electrolysis on Hg and electrolysis catalyzed by radical anions. Various mixtures of CO and oxalate were produced in direct electrolysis.…”

Section: Aromatic Nitriles and Esters As Catalystsmentioning

confidence: 99%

Organic molecules as mediators and catalysts for photocatalytic and electrocatalytic CO₂reduction

2013

Chem. Soc. Rev.

250

169

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Reduction of CO 2 by electrochemical and photoelectrochemical methods to produce carbon-rich fuels is a heavily pursued research theme. Most of the current efforts are focused on the development of transition-metal-based catalysts. In this tutorial review, we present an overview of the development of organic molecules as mediators and catalysts for CO 2 reduction. Four classes of organic molecules are discussed: tetraalkylammonium salts, aromatic esters and nitriles, ionic liquids, and pyridinium derivatives. It is shown that reactions mediated or catalyzed by these organic molecules can be competitive compared to their metal-catalyzed counterparts, both in terms of product selectivity and energy efficiency.

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Mechanism of the electrochemical reduction of carbon dioxide at inert electrodes in media of low proton availability

Cited by 197 publications

References 28 publications

Lithium Oxalate as Capacity and Cycle-Life Enhancer in LNMO/Graphite and LNMO/SiG Full Cells

Lithium Oxalate as Capacity and Cycle-Life Enhancer in LNMO/Graphite and LNMO/SiG Full Cells

Enhanced Electrochemical Methanation of Carbon Dioxide with a Dispersible Nanoscale Copper Catalyst

Organic molecules as mediators and catalysts for photocatalytic and electrocatalytic CO₂reduction

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Mechanism of the electrochemical reduction of carbon dioxide at inert electrodes in media of low proton availability

Cited by 197 publications

References 28 publications

Lithium Oxalate as Capacity and Cycle-Life Enhancer in LNMO/Graphite and LNMO/SiG Full Cells

Lithium Oxalate as Capacity and Cycle-Life Enhancer in LNMO/Graphite and LNMO/SiG Full Cells

Enhanced Electrochemical Methanation of Carbon Dioxide with a Dispersible Nanoscale Copper Catalyst

Organic molecules as mediators and catalysts for photocatalytic and electrocatalytic CO2reduction

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Organic molecules as mediators and catalysts for photocatalytic and electrocatalytic CO₂reduction