Thermodynamics and kinetics of CO2, CO, and H+ binding to the metal centre of CO2reductioncatalysts

Schneider, Jacob; Jia, Hongfei; Muckerman, James T.; Fujita, Etsuko

doi:10.1039/c1cs15278e

Cited by 679 publications

(605 citation statements)

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“…First, negligible CO product was detected in an illuminated acetonitrile solution containing only 0.2 mM Ir(ppy) 3 photosensitizer and 0.07 M TEA in the absence of catalyst 1c. Additionally, solutions containing the simple nickel salt [Ni(MeCN) 6 ] 2+ or the free ligand 1b did not produce comparable activity to the nickel complex 1c. Control experiments without photosensitizer or quencher also showed negligible CO generation under photochemical irradiation, and no CO was produced in a dark reaction with all components added.…”

Section: Resultsmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9][10] In this context, the photocatalytic reduction of CO 2 is an attractive route that can take advantage of the renewable and abundant energy of the sun for longterm CO 2 utilization, 6,11-13 with the eventual target of coupling the reductive half-reaction of CO 2 fixation with a matched oxidative half-reaction such as water oxidation to achieve a carbon-neutral artificial photosynthesis cycle. 14-21 Before this ultimate goal can be realized, however, a host of basic scientific challenges must be addressed, including developing systems that balance selectivity, efficiency, and cost.…”

Section: Introductionmentioning

confidence: 99%

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Visible-Light Photoredox Catalysis: Selective Reduction of Carbon Dioxide to Carbon Monoxide by a Nickel N-Heterocyclic Carbene–Isoquinoline Complex

et al. 2013

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ABSTRACT:The solar-driven reduction of carbon dioxide to value-added chemical fuels is a longstanding challenge in the fields of catalysis, energy science, and green chemistry. In order to develop effective CO 2 fixation, several key considerations must be balanced, including: (1) catalyst selectivity for promoting CO 2 reduction over competing hydrogen generation from proton reduction, (2) visible-light harvesting that matches the solar spectrum, and (3) the use of cheap and earth-abundant catalytic components. In this report, we present the synthesis and characterization of a new family of earthabundant nickel complexes supported by N-heterocyclic carbene-amine ligands that exhibit high selectivity and activity for the electrocatalytic and photocatalytic conversion of CO 2 to CO. Systematic changes in the carbene and amine donors of the ligand have been surveyed, and [Ni( Pr bimiq1)] 2+ (where Pr bimiq1 = bis(3-(imidazolyl)isoquinolinyl)propane, 1c) emerges as a catalyst for electrochemical reduction of CO 2 with the lowest cathodic onset potential (E cat = −1.2 V vs. SCE). Using this earthabundant catalyst with Ir(ppy) 3 (where ppy = 2-phenylpyridine) and an electron donor, we have developed a visible-light photoredox system for the catalytic conversion of CO 2 to CO that proceeds with high selectivity and activity and achieves turnover numbers and turnover frequencies reaching 98,000 and 3.9 s -1 , respectively. Further studies reveal that the overall efficiency of this solar-to-fuel cycle may be limited by the formation of the active Ni catalyst and/or the chemical reduction of CO 2 to CO at the reduced nickel center and provide a starting point for improved photoredox systems for sustainable carbon-neutral energy conversion. 3 IntroductionThe search for sustainable resources has attracted broad interest in the potential use of carbon dioxide as a feedstock for fuels and fine chemicals. [1][2][3][4][5][6][7][8][9][10] In this context, the photocatalytic reduction of CO 2 is an attractive route that can take advantage of the renewable and abundant energy of the sun for longterm CO 2 utilization, 6,11-13 with the eventual target of coupling the reductive half-reaction of CO 2 fixation with a matched oxidative half-reaction such as water oxidation to achieve a carbon-neutral artificial photosynthesis cycle. 14-21 Before this ultimate goal can be realized, however, a host of basic scientific challenges must be addressed, including developing systems that balance selectivity, efficiency, and cost. With regard to selectivity, it is critical to minimize the competitive reduction of water to hydrogen that is typically kinetically favored over CO 2 reduction, as well as selectively convert CO 2 to one carbon product. 22,23 Another primary consideration is the use of visible-light excitation, which more effectively harvests the solar spectrum and avoids deleterious high-energy photochemical pathways. Semiconductors such as TiO 2 and SiC have been widely employed as heterogeneous catalysts for photochemical and photoe...

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Visible-Light Photoredox Catalysis: Selective Reduction of Carbon Dioxide to Carbon Monoxide by a Nickel N-Heterocyclic Carbene–Isoquinoline Complex

et al. 2013

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“…Efficient catalysis of transformations of energy consequence (7)(8)(9)(10)(11)(12)(13) mandates the coupling of electron transfer (ET) to proton transfer (PT) in proton-coupled electron transfer (PCET) reactions (14)(15)(16)(17)(18)(19)(20). In the absence of PCET, intermediates possessing equilibrium potentials that are prohibitively large depreciate the storage capacity offered by the solarto-fuels conversion process.…”

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confidence: 99%

Role of pendant proton relays and proton-coupled electron transfer on the hydrogen evolution reaction by nickel hangman porphyrins

Bediako

Solis

Dogutan

et al. 2014

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

181

204

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The hangman motif provides mechanistic insights into the role of pendant proton relays in governing proton-coupled electron transfer (PCET) involved in the hydrogen evolution reaction (HER). We now show improved HER activity of Ni compared with Co hangman porphyrins. Cyclic voltammogram data and simulations, together with computational studies using density functional theory, implicate a shift in electrokinetic zone between Co and Ni hangman porphyrins due to a change in the PCET mechanism. Unlike the Co hangman porphyrin, the Ni hangman porphyrin does not require reduction to the formally metal(0) species before protonation by weak acids in acetonitrile. We conclude that protonation likely occurs at the Ni(I) state followed by reduction, in a stepwise proton transfer-electron transfer pathway. Spectroelectrochemical and computational studies reveal that upon reduction of the Ni(II) compound, the first electron is transferred to a metal-based orbital, whereas the second electron is transferred to a molecular orbital on the porphyrin ring.renewable | solar fuels | electrocatalysis S olar-to-fuels conversions provide a path to harnessing the ubiquitous albeit intermittent renewable energy resource offered by the sun (1-6). Efficient catalysis of transformations of energy consequence (7-13) mandates the coupling of electron transfer (ET) to proton transfer (PT) in proton-coupled electron transfer (PCET) reactions (14)(15)(16)(17)(18)(19)(20). In the absence of PCET, intermediates possessing equilibrium potentials that are prohibitively large depreciate the storage capacity offered by the solarto-fuels conversion process. The coupling of protons to changes in electron equivalency offers the possibility of restricting the equilibrium potentials of the redox steps to a more narrow potential range, thereby minimizing the overpotential required to sustain catalysis at a desired turnover rate. Thus, the exploitation of PCET pathways to permit potential-leveling effects is a crucial prerequisite for the efficient catalytic conversion reactions of energy relevant molecules.PCET reactions may be classified into stepwise and concerted pathways (14,16,20,21). Stepwise PCET may involve ET first followed by PT (ETPT), or PT followed by ET (PTET). In concerted proton-electron transfers (CPET), the proton and electron traverse a common transition state. Whereas concerted pathways avoid the formation of thermodynamically costly intermediates, CPET reactions may incur kinetic penalties associated with the requirements for proton tunneling (19,20,22). The competition between these dynamics during catalysis determines the most efficient route of reaction. Studies that explore the interplay between these factors are crucial to designing catalytic reactions of high efficiency. Along these lines, the incorporation of proton relays in the second coordination sphere of molecular catalysts has emerged as a useful tool in optimizing PCET transformations (23-29). We have focused on the synthesis and mechanistic investigation of a class of me...

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“…Since the 1970s, many plausible strategies have proved that CO 2 can be converted by chemical methods [5], by photocatalytic and electrocatalytic reduction [6], and by other methodologies [7]. However, after decades of investigation, there are still obstacles that hinder the practical application of transforming CO 2 into value-added materials and fuels.…”

Section: Introductionmentioning

confidence: 99%

Recent Advances in Transition-Metal-Mediated Electrocatalytic CO2 Reduction: From Homogeneous to Heterogeneous Systems

et al. 2017

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Abstract:Global climate change and increasing demands for clean energy have brought intensive interest in the search for proper electrocatalysts in order to reduce carbon dioxide (CO 2 ) to higher value carbon products such as hydrocarbons. Recently, transition-metal-centered molecules or organic frameworks have been reported to show outstanding electrocatalytic activity in the liquid phase. Their d-orbital electrons are believed to be one of the key factors to capture and convert CO 2 molecules to value-added low-carbon fuels. In this review, recent advances in electrocatalytic CO 2 reduction have been summarized based on the targeted products, ranging from homogeneous reactions to heterogeneous ones. Their advantages and fallbacks have been pointed out and the existing challenges, especially with respect to the practical and industrial application are addressed.

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Thermodynamics and kinetics of CO2, CO, and H+ binding to the metal centre of CO2reductioncatalysts

Cited by 679 publications

References 58 publications

Visible-Light Photoredox Catalysis: Selective Reduction of Carbon Dioxide to Carbon Monoxide by a Nickel N-Heterocyclic Carbene–Isoquinoline Complex

Visible-Light Photoredox Catalysis: Selective Reduction of Carbon Dioxide to Carbon Monoxide by a Nickel N-Heterocyclic Carbene–Isoquinoline Complex

Role of pendant proton relays and proton-coupled electron transfer on the hydrogen evolution reaction by nickel hangman porphyrins

Recent Advances in Transition-Metal-Mediated Electrocatalytic CO2 Reduction: From Homogeneous to Heterogeneous Systems

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