Selectivity of CO2, carbonic acid and bicarbonate electroreduction over Iron-porphyrin catalyst: A DFT study

Khakpour, Reza; Laasonen, Kari; Busch, Michael

doi:10.1016/j.electacta.2022.141784

Cited by 12 publications

(22 citation statements)

References 80 publications

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“…− and CO 3 2− dominate the equilibrium at neutral to alkaline pH, while CO 2 and H 2 CO 3 dominate at acidic pH. According to our previous studies, 21,24 bicarbonate is one of the key reactants in CO 2 reduction reactions over Fe porphyrins. Accordingly, it is necessary to consider bicarbonate or carbonic acid reduction when studying the CO 2 reduction reaction in an aqueous solution.…”

Section: ■ Introductionmentioning

confidence: 78%

“…To determine the active form of PcFe under the reaction conditions (pH = 7), pure electron transfer without protonation was calculated. , According to our computations, the reduction of formal PcFe(“II”) to PcFe(“I”) by electron transfer requires a potential of −0.48 V (Figure b). Upon receiving the second electron, PcFe(“I”) forms PcFe(“0”) at a potential of −0.73 V. In a subsequent step, PcFe(“0”) is reduced to PcFe(“-I”) at −0.91 V (Figure b).…”

Section: Resultsmentioning

confidence: 99%

“…In PcFe–COO, H 3 O + prefers to attack the highly nucleophilic oxygen rather than the carbon. ,− Thus, PcFe–COO is reduced through a PCET to the oxygen atom to form PcFe–COOH. This reaction proceeds on PcFe(“I”) and PcFe(“0”) already at relatively high potentials of −0.45 and −0.47 V (Figure ; right arrow).…”

Section: Resultsmentioning

confidence: 99%

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Mechanism of CO₂ Electroreduction to Multicarbon Products over Iron Phthalocyanine Single-Atom Catalysts

Khakpour,

Farshadfar,

Dong

et al. 2024

J. Phys. Chem. C

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Carbon dioxide reduction reaction (CO 2 RR) is a promising method for converting CO 2 into value-added products. CO 2 RR over single-atom catalysts (SACs) is widely known to result in chemical compounds such as carbon monoxide and formic acid that contain only one carbon atom (C1). Indeed, at least two active sites are commonly believed to be required for C−C coupling to synthesize compounds, such as ethanol and propylene (C 2+ ), from CO 2 . However, experimental evidence suggests that iron phthalocyanine (PcFe), which possesses only a single metal center, can produce a trace amount of C 2+ products. To the best of our knowledge, the mechanism by which C 2+ products are formed over a SAC such as PcFe is still unknown. Using density functional theory (DFT), we analyzed the mechanism of the CO 2 RR to C1 and C 2+ products over PcFe. Due to the high concentration of bicarbonate at pH 7, CO 2 RR competes with HCO 3 − reduction. Our computations indicate that bicarbonate reduction is significantly more favorable. However, the rate of this reaction is influenced by the H 3 O + concentration. For the formation of C 2+ products, our computations reveal that C−C coupling proceeds through the reaction between in situ-formed CO and PcFe("0")−CH 2 or PcFe("-I")−CH 2 intermediates. This reaction step is highly exergonic and requires only low activation energies of 0.44 and 0.24 eV for PcFe("0")−CH 2 and PcFe("-I")−CH 2 . The DFT results, in line with experimental evidence, suggest that C 2+ compounds are produced over PcFe at low potentials whereas CH 4 is still the main post-CO product.

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Section: ■ Introductionmentioning

confidence: 78%

Section: Resultsmentioning

confidence: 99%

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Mechanism of CO₂ Electroreduction to Multicarbon Products over Iron Phthalocyanine Single-Atom Catalysts

Khakpour,

Farshadfar,

Dong

et al. 2024

J. Phys. Chem. C

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“…It is commonly assumed that CO 2 reduction proceeds through the direct activation of CO 2 at the catalyst. , However, recent computational work clearly showed that at least in some systems, direct CO 2 reduction is blocked by a very high activation barrier. , For these systems, bicarbonate (HCO 3 – ) or carbonic acid (H 2 CO 3 ) was identified as the most likely active species. Carbonic acid is coupled to CO 2 through a pH-independent equilibrium…”

Section: Results and Discussionmentioning

confidence: 99%

“…showed that at least in some systems, direct CO 2 reduction is blocked by a very high activation barrier. 39,40 For these systems, bicarbonate (HCO 3 − ) or carbonic acid (H 2 CO 3 ) was identified as the most likely active species. Carbonic acid is coupled to CO 2 through a pH-independent equilibrium.…”

Section: ■ Introductionmentioning

confidence: 99%

Exploring the Mechanism of the Electrochemical Polymerization of CO₂ to Hard Carbon over CeO₂(110)

Keller,

Döhn,

Groß

et al. 2024

J. Phys. Chem. C

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Conversion of CO 2 to hard carbon is an interesting technology for the removal of carbon dioxide from the atmosphere. Recently, it was shown that CeO 2 can selectively catalyze this reaction, but we still lack information regarding the reaction mechanism. Using density functional theory modeling, we explore possible reaction mechanisms that allow for the polymerization of CO 2 . According to our computations, the reaction is initialized by the adsorption of CO 2 in an oxygen vacancy. Owing to the rich defect chemistry of ceria, a large number of suitable sites are available at the surface. C−C bond formation is achieved through an aldol condensation-type mechanism which comprises the electrochemical elimination of water to form a carbene. This carbene then performs a nucleophilic attack on CO 2 . The reaction mechanism possesses significant similarities to the corresponding reactions in synthetic organic chemistry. Since the mechanism is completely generic, it allows for all relevant steps of the formation of hard carbon like chain growth, chain linkage, and the formation of side chains or aromatic rings. Surprisingly, ceria mainly serves as an anchor for CO 2 in an oxygen vacancy, while all other subsequent reaction steps are almost completely independent from the catalyst. These insights are important for the development of novel catalysts for CO 2 reduction and may also lead to new reactions for the electrosynthesis of organic molecules.

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Mechanism of CO₂ Reduction to Methanol with H₂ on an Iron(II)‐scorpionate Catalyst

Zhu,

D'Agostino,

de Visser

2023

Chemistry A European J

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CO2 utilization is an important process in the chemical industry with great environmental power. In this work we show how CO2 and H2 can be reacted to form methanol on an iron(II) center and highlight the bottlenecks for the reaction and what structural features are essential for efficient turnover. The calculations predict the reactions to proceed through three successive reaction cycles that start with heterolytic cleavage of H2 followed by sequential hydride and proton transfer processes. The H2 splitting process is an endergonic process and hence high pressures will be needed to overcome this step and trigger the hydrogenation reaction. Moreover, H2 cleavage into a hydride and proton requires a metal to bind hydride and a nearby source to bind the proton, such as an amide or pyrazolyl group, which the scorpionate ligand used here facilitates. As such the computations highlight the non‐innocence of the ligand scaffold through proton shuttle from H2 to substrate as an important step in the reaction mechanism.

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Selectivity of CO2, carbonic acid and bicarbonate electroreduction over Iron-porphyrin catalyst: A DFT study

Cited by 12 publications

References 80 publications

Mechanism of CO₂ Electroreduction to Multicarbon Products over Iron Phthalocyanine Single-Atom Catalysts

Mechanism of CO₂ Electroreduction to Multicarbon Products over Iron Phthalocyanine Single-Atom Catalysts

Exploring the Mechanism of the Electrochemical Polymerization of CO₂ to Hard Carbon over CeO₂(110)

Mechanism of CO₂ Reduction to Methanol with H₂ on an Iron(II)‐scorpionate Catalyst

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Selectivity of CO2, carbonic acid and bicarbonate electroreduction over Iron-porphyrin catalyst: A DFT study

Cited by 12 publications

References 80 publications

Mechanism of CO2 Electroreduction to Multicarbon Products over Iron Phthalocyanine Single-Atom Catalysts

Mechanism of CO2 Electroreduction to Multicarbon Products over Iron Phthalocyanine Single-Atom Catalysts

Exploring the Mechanism of the Electrochemical Polymerization of CO2 to Hard Carbon over CeO2(110)

Mechanism of CO2 Reduction to Methanol with H2 on an Iron(II)‐scorpionate Catalyst

Contact Info

Product

Resources

About

Mechanism of CO₂ Electroreduction to Multicarbon Products over Iron Phthalocyanine Single-Atom Catalysts

Mechanism of CO₂ Electroreduction to Multicarbon Products over Iron Phthalocyanine Single-Atom Catalysts

Exploring the Mechanism of the Electrochemical Polymerization of CO₂ to Hard Carbon over CeO₂(110)

Mechanism of CO₂ Reduction to Methanol with H₂ on an Iron(II)‐scorpionate Catalyst