Reaction Diffusion Modelling of 3D Pillar Electrodes in Single-Catalyst CO2 Reduction Cascades

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  • Fernandez, Pablo
    • College of Arts and Sciences, Department of Chemistry
  • García-Batlle, Marisé
    • College of Arts and Sciences, Department of Chemistry
  • Shang, Bo
    • Other Affiliation: Department of Chemistry, Yale University, New Haven, CT
  • Wang, Hailiang
    • Other Affiliation: Department of Chemistry, Yale University, New Haven, CT
  • Parsons, Gregory N.
    • Other Affiliation: Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC
  • Cahoon, James F.
    • College of Arts and Sciences, Department of Physics and Astronomy
  • Lopez, Rene
    • College of Arts and Sciences, Department of Physics and Astronomy
Abstract
  • Effective electrochemical CO2 reduction to liquid fuels requires that the local catalytic environment facilitates the desired reactivity, yet a microscopic understanding of this environment is difficult to achieve from experiment alone. In this work, a 3D reaction-diffusion model was developed to explore the effects of electrode surface area and local geometry on the performance of a heterogeneous catalyst that performs a two-step CO2 reduction cascade reaction to CO and then CH3OH under aqueous conditions. Kinetic parameters for the model were inspired by experimental results using a cobalt phthalocyanine (CoPc) catalyst. Three-dimensional architectures composed of arrays of square pillars with varying dimensions and either smooth or periodically modulated surfaces were tested, revealing the extent to which geometry modulates the performance of the cascade reactions. Although structural variations modulate local concentration gradients, we find that electrochemically active surface area predominantly governs the overall cascade reaction. Moreover, the results suggest that supersaturation of CO, with concentrations up to ten-fold higher than the equilibrium solubility limit, might be critical for more efficient conversion to CH3OH. For any given geometry, the spatially averaged ratio of [CO] to [CO2] is dictated by the electrochemically active surface area and determines the yield of CH3OH. For a fixed surface area, geometries that spatially confine the electrolyte yield moderate local [CO] to [CO2] ratios within small volumes. In contrast, less confining geometries result in a broader distribution of local ratios spread over larger volumes, with both configurations yielding the same spatially averaged [CO] to [CO2] ratio. These insights provide valuable design principles—highlighting the critical importance of surface area and possibly CO supersaturation—for engineering advanced electrode architectures that leverage intermediate trapping and CO supersaturation to enhance overall performance in tandem CO2 reduction systems.
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  • Attribution 4.0 International
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  • Electrochem
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  • English
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  • 2673-3293
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  • Multidisciplinary Digital Publishing Institute

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