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Abstract Cobalt phthalocyanine (CoPc) is a promising molecular catalyst for aqueous electroreduction of CO2, but its catalytic activity is limited by aggregation at high loadings. Codeposition of CoPc onto electrode surfaces with the coordinating polymer poly(4‐vinylpyridine) (P4VP) mitigates aggregation in addition to providing other catalytic enhancements. Transmission and diffuse reflectance UV–vis measurements demonstrate that a combination of axial coordination and π‐stacking effects from pyridyl moieties in P4VP serve to disperse cobalt phthalocyanine in deposition solutions and help prevent reaggregation in deposited films. Polymers lacking axial coordination, such as Nafion, are significantly less effective at cobalt phthalocyanine dispersion in both the deposition solution and in the deposited films. SEM images corroborate these findings through particle counts and morphological analysis. Electrochemical measurements show that CoPc codeposited with P4VPonto carbon electrode surfaces reduces CO2with higher activity and selectivity compared to the catalyst codeposited with Nafion.
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Enhancing CO2 Reduction Efficiency on Cobalt Phthalocyanine via Axial Ligation
Electrochemical reduction of carbon dioxide (CO2RR) to value-added products is a promising strategy to alleviate the greenhouse gas effect. Molecular catalysts, such as cobalt (II) phthalocyanine (CoPc), are known to be efficient electrocatalysts that are capable of converting CO2 into carbon monoxide (CO). Herein, we report an axial modification strategy to enhance CoPc’s CO2RR performance. After coordinating with axial ligands, the electron density of Co was depleted via π-backbonding. This π-backbonding weakened the Co-CO bond, resulting in rapid desorption of CO. Also, the presence axial ligands elevated the Co dz2 orbital energy, resulting in a significantly enhanced CO2 selectivity, evidenced by an increased faradaic efficiency (FE) from 82% (CoPc) to 91% (pyridine) and 94% (imidazole) at -0.82 V vs. RHE. Density functional theory calculations reveal that axial ligation of CoPc can reduce the energy barrier for CO2 activation and facilitate the formation of *COOH.
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- PAR ID:
- 10425078
- Date Published:
- Journal Name:
- ChemCatChem
- ISSN:
- 1867-3880
- 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/10.1002/cctc.202300576
