Turning it off! Disfavouring hydrogen evolution to enhance selectivity for CO production during homogeneous CO<sub>2</sub> reduction by cobalt–terpyridine complexes

Elgrishi, Noémie; Chambers, Matthew B.; Fontecave, Marc

doi:10.1039/c4sc03766a

Cited by 168 publications

(130 citation statements)

References 44 publications

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“…These mechanistic insights predict that CDR selectivity can be enhanced over a wider potential range by amplifying proton depletion effects within a porous electrode, a notion supported by our recent studies on ordered porous Au inverse opals (41). Interestingly, similar suppression of HER has been shown to enhance CDR selectivity in molecular catalytic systems (102).…”

Section: Concludingsupporting

confidence: 50%

Inhibited proton transfer enhances Au-catalyzed CO ₂ -to-fuels selectivity

Wuttig

Yaguchi

Motobayashi

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

369

480

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CO 2 reduction in aqueous electrolytes suffers efficiency losses because of the simultaneous reduction of water to H 2 . We combine in situ surface-enhanced IR absorption spectroscopy (SEIRAS) and electrochemical kinetic studies to probe the mechanistic basis for kinetic bifurcation between H 2 and CO production on polycrystalline Au electrodes. Under the conditions of CO 2 reduction catalysis, electrogenerated CO species are irreversibly bound to Au in a bridging mode at a surface coverage of ∼0.2 and act as kinetically inert spectators. Electrokinetic data are consistent with a mechanism of CO production involving rate-limiting, single-electron transfer to CO 2 with concomitant adsorption to surface active sites followed by rapid one-electron, two-proton transfer and CO liberation from the surface. In contrast, the data suggest an H 2 evolution mechanism involving rate-limiting, single-electron transfer coupled with proton transfer from bicarbonate, hydronium, and/or carbonic acid to form adsorbed H species followed by rapid one-electron, one-proton, or H recombination reactions. The disparate proton coupling requirements for CO and H 2 production establish a mechanistic basis for reaction selectivity in electrocatalytic fuel formation, and the high population of spectator CO species highlights the complex heterogeneity of electrode surfaces under conditions of fuel-forming electrocatalysis.carbon dioxide reduction | catalyst selectivity | in situ spectroscopy | proton-coupled electron transfer P roduct selectivity is a principal design consideration for the development of practical catalysts. Catalyst selectivity is dictated by (i) the relative free energy barriers for progress along competing reaction pathways and (ii) the relative rates of reactant delivery to active sites (1). Enzymes fine tune these parameters with exquisite precision to achieve selectivity (2). Nature augments the coordination environment of metallocofactor active sites to optimize the binding strengths of reaction partners and preorganizes reaction participants toward low-barrier pathways (3). Additionally, many active sites reside at the terminus of molecular channels that gate the coordinated delivery of substrates (4, 5) required for selective transformations. Efforts to prepare artificial catalysts with product selectivities rivaling that of nature require a detailed understanding of these factors.Currently, our understanding of how to systematically modulate selectivity in heterogeneous catalysts remains poor (6-8). Unlike (bio)molecular catalysts, which ideally consist of a uniform ensemble of active sites, heterogeneous catalysts consist of a nonuniform distribution of surface sites (9), requiring an understanding of which are active and which are dormant. The surface site distribution is strongly dependent on the surface nanostructure, oxidation state, and degree of restructuring (7). Superimposed on this distribution are the rate-limiting elementary reaction steps that dictate kinetic branching ratios at surface active sites (1...

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Section: Concludingsupporting

confidence: 50%

Inhibited proton transfer enhances Au-catalyzed CO ₂ -to-fuels selectivity

Wuttig

Yaguchi

Motobayashi

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

369

480

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“…The resonance Raman data of intermediate I, which could only be stabilized at -95 o C, indicates that it is a Fe(II)-CO2 2- Mitigation of CO2 and assimilating it into useful chemicals is an urgent challenge in the context of growing concerns over the green house effect of CO2 and depleting fossil fuels. 1,[2][3][4] Substantial focus is on the effective reduction of CO2 into CO and other essential products. [5][6][7] The direct reduction of CO2 to CO2 .-is highly energy demanding and occurs at fairly negative potential (-1.9 V vs SHE in acetonitrile).…”

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confidence: 99%

Intermediates Involved in the 2e^–/2H⁺ Reduction of CO₂ to CO by Iron(0) Porphyrin

et al. 2015

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The reduction of CO2 by an iron porphyrin complex with a hydrogen bonding distal pocket involves at least two intermediates. The resonance Raman data of intermediate I, which could only be stabilized at -95 °C, indicates that it is a Fe(II)-CO2(2-) adduct and is followed by an another intermediate II at -80 °C where the bound CO2 in intermediate I is protonated to form a Fe(II)-COOH species. While the initial protonation can be achieved using weak proton sources like MeOH and PhOH, the facile heterolytic cleavage of the C-OH bond in intermediate II requires strong acids.

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“…Cyclic voltammetry (CV) performed on a solution of in CH3CN ( Figure 2) displays two successive reversible electron transfer waves, which can be tentatively assigned to a metal centered Co(II)/Co(I) process (E1/2 = -1.1 V, all potentials vs. Ag/AgCl) and to a ligand centered reduction (E1/2 = -1.61 V). [8,11] Noteworthly, in contrast to all known Co polypyridine complexes, no Co(III)/Co(II) wave was observed until +2.0 V (i.e. in the range of the solvent electrochemical window).…”

mentioning

confidence: 99%

“…730 mV at the second one (see Section 4 of Supporting Information for calculations details). [8,[11][12] Cyclic . The quantum yield values obtained using 0.1 M and 10 M of catalyst are estimated to be 3% and 11% respectively (see Section 15 of Supporting Information).…”

mentioning

confidence: 99%

Heptacoordinate Co^II Complex: A New Architecture for Photochemical Hydrogen Production

Lucarini

Pastore

Vasylevskyi

et al. 2017

Chemistry A European J

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The first heptacoordinate cobalt catalyst for light‐driven hydrogen production in water has been synthesized and characterized. Photochemical experiments using [Ru(bpy)3]2+ as photosensitizer gave a turnover number (TON) of 16300 mol H2 (mol cat.)−1 achieved in 2 hours of irradiation with visible (475 nm) light. This promising result provides a path forward in the development of new structures to improve the efficiency of the catalysis.

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Turning it off! Disfavouring hydrogen evolution to enhance selectivity for CO production during homogeneous CO₂ reduction by cobalt–terpyridine complexes

Abstract: Understanding the activity and selectivity of molecular catalysts for CO2 reduction to fuels is an important scientific endeavour in addressing the growing global energy demand.

Cited by 168 publications

References 44 publications

Inhibited proton transfer enhances Au-catalyzed CO ₂ -to-fuels selectivity

Inhibited proton transfer enhances Au-catalyzed CO ₂ -to-fuels selectivity

Intermediates Involved in the 2e^–/2H⁺ Reduction of CO₂ to CO by Iron(0) Porphyrin

Heptacoordinate Co^II Complex: A New Architecture for Photochemical Hydrogen Production

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Turning it off! Disfavouring hydrogen evolution to enhance selectivity for CO production during homogeneous CO2 reduction by cobalt–terpyridine complexes

Abstract: Understanding the activity and selectivity of molecular catalysts for CO2 reduction to fuels is an important scientific endeavour in addressing the growing global energy demand.

Cited by 168 publications

References 44 publications

Inhibited proton transfer enhances Au-catalyzed CO 2 -to-fuels selectivity

Inhibited proton transfer enhances Au-catalyzed CO 2 -to-fuels selectivity

Intermediates Involved in the 2e–/2H+ Reduction of CO2 to CO by Iron(0) Porphyrin

Heptacoordinate CoII Complex: A New Architecture for Photochemical Hydrogen Production

Contact Info

Product

Resources

About

Turning it off! Disfavouring hydrogen evolution to enhance selectivity for CO production during homogeneous CO₂ reduction by cobalt–terpyridine complexes

Inhibited proton transfer enhances Au-catalyzed CO ₂ -to-fuels selectivity

Inhibited proton transfer enhances Au-catalyzed CO ₂ -to-fuels selectivity

Intermediates Involved in the 2e^–/2H⁺ Reduction of CO₂ to CO by Iron(0) Porphyrin

Heptacoordinate Co^II Complex: A New Architecture for Photochemical Hydrogen Production