E.N. Butt
info
Please Note
<p>This page displays the records of the person named above and is not linked to a unique person identifier. This record may need to be merged to a profile.</p>
4 records found
1
We demonstrate that pulsed electrolysis can unlock higher performance in CO2 electroreduction (CO2ER) on gas diffusion electrodes (GDEs), which we find are limited by cation-induced CO2 depletion and reduced Faradaic efficiency (FE) at high cathodic potentials. Using continuum-scale modeling, we show that pulsing strategies significantly enhance current density compared to steady-state operation at the same mean potential. Thicker catalyst layers (CLs) particularly benefit from pulsed electrolysis, achieving higher current densities near the gas/liquid interface along with overall improvements in Faradaic and cathodic efficiency compared to constant-potential systems. This is caused by the prolonged time for the cations to transport back to and block the catalytic surface, which improves CO2 accessibility. Tuning the pulse parameters, especially with unequal durations, results in a similar current density as a constant potential system, but with better Faradaic and cathodic efficiency. These findings underscore pulsed electrolysis as a scalable and effective method to enhance CO2ER performance in GDE systems, offering practical improvements for industrial applications.
...
We demonstrate that pulsed electrolysis can unlock higher performance in CO2 electroreduction (CO2ER) on gas diffusion electrodes (GDEs), which we find are limited by cation-induced CO2 depletion and reduced Faradaic efficiency (FE) at high cathodic potentials. Using continuum-scale modeling, we show that pulsing strategies significantly enhance current density compared to steady-state operation at the same mean potential. Thicker catalyst layers (CLs) particularly benefit from pulsed electrolysis, achieving higher current densities near the gas/liquid interface along with overall improvements in Faradaic and cathodic efficiency compared to constant-potential systems. This is caused by the prolonged time for the cations to transport back to and block the catalytic surface, which improves CO2 accessibility. Tuning the pulse parameters, especially with unequal durations, results in a similar current density as a constant potential system, but with better Faradaic and cathodic efficiency. These findings underscore pulsed electrolysis as a scalable and effective method to enhance CO2ER performance in GDE systems, offering practical improvements for industrial applications.
The pressing need to address climate change and resource sustainability has catalyzed interest in technologies that can effectively mitigate CO2 emissions. Electrochemical reduction of CO2 is one such technology, offering a pathway to convert CO2 into valuable chemicals and fuels using renewable electricity. Despite its promise, the industrial application of CO2 electrolysis faces significant challenges, including limited mass transport, inefficient reaction kinetics, and poor control over the local reaction environment at the catalyst interface. This dissertation tackles these challenges through advanced numerical modeling. The research identifies key bottlenecks, such as CO2 solubility limits and local pH shifts, and explores strategies to overcome them using innovative electrode designs and operation modes. By extending the Poisson–Nernst–Planck framework to include finite size effects and the Frumkin-corrected Tafel relation, this work provides a detailed understanding of the electric double layer, steric effects, and solvent dynamics near the catalyst surface for H-cell configurations. These models are validated against experimental data, ensuring their robustness and applicability. Gas diffusion electrodes offer significant advantages over traditional H-cell systems by enabling direct CO2 delivery to the reaction site. However, these systems introduce new complexities, such as the interplay between pore structure, ion transport, and local reaction conditions. By simulating the behavior of these gas diffusion electrodes under various operating conditions, the research identifies optimal configurations for an ideal local reaction environment, thus paving the way for more efficient CO2 conversion. A novel aspect of this dissertation is the exploration of dynamic pulsed potential systems. These modes allow better control over product selectivity by leveraging transient reaction environments. The insights gained from these studies not only improve our understanding of CO2 electrolysis mechanisms but also provide practical guidelines for scaling up the technology. The work concludes by presenting a roadmap for the development of scalable, sustainable CO2 electroreduction systems. It emphasizes the importance of integrating experimental and computational approaches to tackle the multiscale challenges inherent in CO2 electrolysis. The models developed here serve as powerful tools for predicting system performance, designing next-generation reactors, and accelerating the transition to industrial-scale applications. The findings contribute to the broader effort of developing technologies that enable a circular carbon economy, thereby addressing global energy and environmental challenges.
...
The pressing need to address climate change and resource sustainability has catalyzed interest in technologies that can effectively mitigate CO2 emissions. Electrochemical reduction of CO2 is one such technology, offering a pathway to convert CO2 into valuable chemicals and fuels using renewable electricity. Despite its promise, the industrial application of CO2 electrolysis faces significant challenges, including limited mass transport, inefficient reaction kinetics, and poor control over the local reaction environment at the catalyst interface. This dissertation tackles these challenges through advanced numerical modeling. The research identifies key bottlenecks, such as CO2 solubility limits and local pH shifts, and explores strategies to overcome them using innovative electrode designs and operation modes. By extending the Poisson–Nernst–Planck framework to include finite size effects and the Frumkin-corrected Tafel relation, this work provides a detailed understanding of the electric double layer, steric effects, and solvent dynamics near the catalyst surface for H-cell configurations. These models are validated against experimental data, ensuring their robustness and applicability. Gas diffusion electrodes offer significant advantages over traditional H-cell systems by enabling direct CO2 delivery to the reaction site. However, these systems introduce new complexities, such as the interplay between pore structure, ion transport, and local reaction conditions. By simulating the behavior of these gas diffusion electrodes under various operating conditions, the research identifies optimal configurations for an ideal local reaction environment, thus paving the way for more efficient CO2 conversion. A novel aspect of this dissertation is the exploration of dynamic pulsed potential systems. These modes allow better control over product selectivity by leveraging transient reaction environments. The insights gained from these studies not only improve our understanding of CO2 electrolysis mechanisms but also provide practical guidelines for scaling up the technology. The work concludes by presenting a roadmap for the development of scalable, sustainable CO2 electroreduction systems. It emphasizes the importance of integrating experimental and computational approaches to tackle the multiscale challenges inherent in CO2 electrolysis. The models developed here serve as powerful tools for predicting system performance, designing next-generation reactors, and accelerating the transition to industrial-scale applications. The findings contribute to the broader effort of developing technologies that enable a circular carbon economy, thereby addressing global energy and environmental challenges.
The local conditions inside a gas diffusion electrode (GDE) pore, especially in the electrical double layer (EDL) region, influence the charge transfer reactions and the selectivity of desired CO2ER products. Most GDE computational models ignore the EDL or are limited in their applicability at high potentials. In this work, we present a continuum model to describe the local environment inside a catalytic pore at varying potentials, electrolyte concentrations and pore diameters. The systems studied in this work are based on an Ag catalyst in contact with KHCO3 solution. Our study shows that steric effects dominate the local environment at high cathodic potentials (≪−25 mV vs pzc at the OHP), leading to a radial drop of CO2 concentration. We also observe a drop in pH value within 1 nm of the reaction plane due to electrostatic repulsion and attraction of OH− and H+ ions, respectively. We studied the influence of pore radii (1-10 nm) on electric field and concentrations. Pores with a radius smaller than 5 nm show a higher mean potential, which lowers the mean CO2 concentration. Pores with a favourable local environment can be designed by regulating the ratio between the pore radius and Debye length.
...
The local conditions inside a gas diffusion electrode (GDE) pore, especially in the electrical double layer (EDL) region, influence the charge transfer reactions and the selectivity of desired CO2ER products. Most GDE computational models ignore the EDL or are limited in their applicability at high potentials. In this work, we present a continuum model to describe the local environment inside a catalytic pore at varying potentials, electrolyte concentrations and pore diameters. The systems studied in this work are based on an Ag catalyst in contact with KHCO3 solution. Our study shows that steric effects dominate the local environment at high cathodic potentials (≪−25 mV vs pzc at the OHP), leading to a radial drop of CO2 concentration. We also observe a drop in pH value within 1 nm of the reaction plane due to electrostatic repulsion and attraction of OH− and H+ ions, respectively. We studied the influence of pore radii (1-10 nm) on electric field and concentrations. Pores with a radius smaller than 5 nm show a higher mean potential, which lowers the mean CO2 concentration. Pores with a favourable local environment can be designed by regulating the ratio between the pore radius and Debye length.
Electrochemical reduction of CO2 heavily depends on the reaction conditions found near the electrode surface. These local conditions are affected by phenomena such as electric double layer formation and steric effects of the solution species, which in turn impact the passage of CO2 molecules to the catalytic surface. Most models for CO2 reduction ignore these effects, leading to an incomplete understanding of the local electrode environment. In this work, we present a modeling approach consisting of a set of size-modified Poisson–Nernst–Planck equations and the Frumkin interpretation of Tafel kinetics. We introduce a modification to the steric effects inside the transport equations which results in more realistic concentration profiles. We also show how the modification lends the model numerical stability without adopting any separate stabilization technique. The model can replicate experimental current densities and faradaic efficiencies till −1.5 vs. SHE/V of applied electrode potential. We also show the utility of this approach for systems operating at elevated CO2 pressures. Using Frumkin-corrected kinetics gels well with the theoretical understanding of the double layer. Hence, this work provides a sound mechanistic understanding of the CO2 reduction process, from which new insights on key performance controlling parameters can be obtained.
...
Electrochemical reduction of CO2 heavily depends on the reaction conditions found near the electrode surface. These local conditions are affected by phenomena such as electric double layer formation and steric effects of the solution species, which in turn impact the passage of CO2 molecules to the catalytic surface. Most models for CO2 reduction ignore these effects, leading to an incomplete understanding of the local electrode environment. In this work, we present a modeling approach consisting of a set of size-modified Poisson–Nernst–Planck equations and the Frumkin interpretation of Tafel kinetics. We introduce a modification to the steric effects inside the transport equations which results in more realistic concentration profiles. We also show how the modification lends the model numerical stability without adopting any separate stabilization technique. The model can replicate experimental current densities and faradaic efficiencies till −1.5 vs. SHE/V of applied electrode potential. We also show the utility of this approach for systems operating at elevated CO2 pressures. Using Frumkin-corrected kinetics gels well with the theoretical understanding of the double layer. Hence, this work provides a sound mechanistic understanding of the CO2 reduction process, from which new insights on key performance controlling parameters can be obtained.