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Electrocatalytic coreduction of carbon dioxide (CO2) and nitrate (NO3–) offers a sustainable route to the synthesis of urea. A major challenge for this reaction is enhancing C–N coupling, which is strongly influenced by catalyst composition and surface morphology. Here, we use grand-canonical density functional theory (GC-DFT) to model how the exposed facet of Ag and Cu electrodes affects the intrinsic kinetics of C–N coupling, comparing stepped (211) and terrace (100, 111) surfaces under applied electrochemical potentials in acidic media. We predict that low-coordination stepped surfaces (211) exhibit superior C–N coupling activity compared to terraces. Linear scaling relations link reaction energies and activation barriers with coadsorption energies for key C–N coupling steps with the coadsorption energies of C- and N-species, providing a thermodynamic descriptor for intermediate coupling. The potential-dependence origins of representative C–N coupling reactions are dominated by capacitive and dipole-field effects, which are larger for CO2 coupling than for CO coupling. These insights reveal why stepped sites are more active for the first C–N coupling step and may guide nanostructuring strategies to design electrocatalysts for CO2–NO3– coreduction.
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Prediction of Potential-Dependent Kinetics for the Electrocatalytic Reduction of CO 2 to CO over Ti@4N-Gr
Grand canonical density functional theory (GC-DFT) was employed to model the electrocatalytic reduction of CO2 (CO2R) to CO by single titanium atom nitrogen-doped graphene, referred to as Ti@4N-Gr. Previous GC-DFT thermodynamic investigations have identified Ti@4N-Gr as a promising CO2R catalyst; however, no in-depth studies have examined it. In this study, we analyze activation energies of the elementary steps at various applied potentials in addition to thermodynamics of CO2R to CO catalyzed by Ti@xN-Gr defects. Reaction intermediates are predicted to be destabilized when Ti is coordinated to fewer N atoms. Based on reaction thermodynamics, Ti@4N-Gr and all defect configurations are predicted to be potentially promising catalysts for CO2R to CO at an applied potential of −0.7 VSHE while at −0.3 and −1.2 VSHE the reaction is predicted to be hindered by relatively large grand free energy differences between intermediates. We propose a criterion to identify optimum applied potentials for CO2R to CO based on the potential of zero charge (PZC) of the reaction intermediates and the contention that the optimum applied potential for CO2R to CO lies in the range PZC∗CO<𝑉
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- Award ID(s):
- 2016225
- PAR ID:
- 10567703
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- ACS Electrochemistry
- ISSN:
- 2997-0571
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1021/acselectrochem.4c00073
