Rate of Absorption of Carbon Dioxide Effect of Concentration and Viscosity of Caustic Solutions

Hitchcock, Lauren B.

doi:10.1021/ie50299a008

Cited by 18 publications

(13 citation statements)

References 7 publications

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“…Further, this reactant gas distribution is apparently regulated by the electrolyte concentration at high current densities (∼100 mA cm –2 ). In the CO 2 case, the CO 2 equilibrium with (bi)carbonate plays an important role, with high local hydroxide concentrations consuming CO 2 , which will limit penetration of CO 2 into the CL. ,, Also, as demonstrated for the ORR, the high electrolyte concentration in the CL will increase the viscosity, thereby slowing diffusion of CO 2 and diminishing the electrolyte conductivity . Thus, the portion of the CL primarily responsible for the CO 2 R current likely extends 10–1000 nm from the gas–liquid interface, with a thinner reaction zone at higher current densities, and a current distribution as depicted in Figure b.…”

Section: Current Distribution In Wet Catalyst Layersmentioning

confidence: 99%

Liquid–Solid Boundaries Dominate Activity of CO₂ Reduction on Gas-Diffusion Electrodes

et al. 2020

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Electrochemical CO2 electrolysis to produce hydrocarbon fuels or material feedstocks offers a renewable alternative to fossilized carbon sources. Gas diffusion electrodes (GDEs), composed of solid electrocatalysts on porous supports positioned near the interface of a conducting electrolyte and CO 2 gas, have been able to demonstrate the substantial current densities needed for future commercialization. These higher reaction rates have often been ascribed to the presence of a three-phase interface, where solid, liquid, and gas provide electrons, water, and CO2, respectively. Conversely, mechanistic work on electrochemical reactions implicates a fully two-phase reaction interface, where gas molecules reach the electrocatalyst's surface by dissolution and diffusion through the electrolyte. Because the discrepancy between an atomistic three-phase vs. two-phase reaction has substantial implications for the design of catalysts, gasdiffusion layers and cell architectures, the nuances of nomenclatures and governing phenomena surrounding the three-phase-region require clarification. Here, we outline the macro, micro and atomistic phenomena occurring within a gas-diffusion electrode to provide a focused discussion on the architecture of the often-discussed three-phase region for CO2 electrolysis. From this information, we comment on the outlook for the broader CO2 electro-reduction GDE cell architecture.

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Section: Current Distribution In Wet Catalyst Layersmentioning

confidence: 99%

Liquid–Solid Boundaries Dominate Activity of CO₂ Reduction on Gas-Diffusion Electrodes

et al. 2020

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“…Experimental studies have been limited almost entirely to gas-liquid systems and rapid irreversible second-order reactions. Thus Stephens and Morris (24) absorbed chlorine by aqueous ferrous chloride in a disk column; Hatta (7), Hitchcock (8), and others absorbed carbon dioxide by aqueous sodium hydroxide in stirred vessels; Vivian and Whitney (26,28) absorbed chlorine and sulfur dioxide by water in packed towers; and van Krevelen and Kreckels (70) dissolved granules of benzoic acid in a packed bed by aqueous solutions of ammonia and sodium hydroxide. Pozin (78) absorbed several acid gases in alkaline solutions and ammonia in acid, using small glass vessels.…”

mentioning

confidence: 99%

Interfacial Phenomena in Liquid Extraction

Sherwood¹,

Wei²

1957

Ind. Eng. Chem.

127

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“…Likewise, well-controlled studies such as that with the ORR at a nanopipette, which singled out the effect of water activity on the ORR, could provide useful information about CO 2 R. This could aid future modeling efforts that attempt to account for variations in water and solute activity. These insights can guide understanding of the diverse multiphase chemistry associated with CO 2 R: carbonate and bicarbonate equilibria, , CO 2 consumption by hydroxide, and multiple simultaneous product activities. These added complexities are absent in ORR, so explicit CO 2 centric studies would be needed.…”

Section: Resultsmentioning

confidence: 99%

Water and Solute Activities Regulate CO₂ Reduction in Gas-Diffusion Electrodes

Nesbitt

Smith

2021

J. Phys. Chem. C

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Electrolysis of CO2 at gas-diffusion electrodes (GDEs) has typically been limited by the supply of gas to the electrocatalyst, overshadowing the importance of the supply of water. However, at high current densities that approach 1 A cm–2, where the electrolyte becomes highly concentrated in the catalyst layer of a GDE, the activity of water and solutes deviate from their bulk dilute solution values, potentially slowing reaction rates and changing reaction equilibrium potentials. In addition, as flow plates for the gas stream are introduced to enable larger electrodes and high single pass conversion of CO2 to product, variations in the gas composition will become important. By drawing upon literature for the oxygen reduction reaction (ORR), here we explain how to account for these effects in future modeling and experimental work, with particular attention to accurate use of the Nernst equation for electrode potentials and the Arrhenius equation for reaction rates. Specifically, using measurements of KOH solvent and solute activity reported in literature, and assuming the second protonation of CO2 by water as the rate-determining step, we show the Nernst equation dilute-solution approximation of the CO2 to CO equilibrium potential to be accurate below 5 M KOH, but it has a 74 mV error when increasing the concentration up to 10 M KOH. Finally, a simple one-dimensional model of a serpentine flow-field on a GDE demonstrated that a reactor with constant pressure of 1 bar and 1 A cm–2 at the inlet had only ∼0.3 A cm–2 at the outlet for a conversion in CO2 partial pressure from 0.90 to 0.48 bar, showing the significant practical implications of this work.

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Rate of Absorption of Carbon Dioxide Effect of Concentration and Viscosity of Caustic Solutions

Cited by 18 publications

References 7 publications

Liquid–Solid Boundaries Dominate Activity of CO₂ Reduction on Gas-Diffusion Electrodes

Liquid–Solid Boundaries Dominate Activity of CO₂ Reduction on Gas-Diffusion Electrodes

Interfacial Phenomena in Liquid Extraction

Water and Solute Activities Regulate CO₂ Reduction in Gas-Diffusion Electrodes

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Rate of Absorption of Carbon Dioxide Effect of Concentration and Viscosity of Caustic Solutions

Cited by 18 publications

References 7 publications

Liquid–Solid Boundaries Dominate Activity of CO2 Reduction on Gas-Diffusion Electrodes

Liquid–Solid Boundaries Dominate Activity of CO2 Reduction on Gas-Diffusion Electrodes

Interfacial Phenomena in Liquid Extraction

Water and Solute Activities Regulate CO2 Reduction in Gas-Diffusion Electrodes

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Product

Resources

About

Liquid–Solid Boundaries Dominate Activity of CO₂ Reduction on Gas-Diffusion Electrodes

Liquid–Solid Boundaries Dominate Activity of CO₂ Reduction on Gas-Diffusion Electrodes

Water and Solute Activities Regulate CO₂ Reduction in Gas-Diffusion Electrodes