Cobalt Carbonyl Clusters Enable Independent Control of Two Proton Transfer Rates in the Mechanism for Hydrogen Evolution

Pattanayak, Santanu; Berben, Louise A.

doi:10.1002/celc.202100402

Cited by 12 publications

(13 citation statements)

References 57 publications

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“…Molecular Tafel plots for selected molecular electrocatalysts for production of H 2 . Conditions: [DMF(H)]NTf 2 –H 2 O with χ H 2 O = 0.7 (1); [DMF(H)] + in adiponitrile with 1.1 M H 2 O (2) and 0.5 M H 2 O (3); [4-F 3 CO-C 6 H 4 NH 3 ] + in MeCN (4); [C 6 H 4 NH 3 ] + in MeCN (5); , Tris buffer (pH 7) in water (6); [Et 3 NH] + in MeCN (7); [Et 3 NH] + in DMF (8) . TOFs are the highest value measured, except for 7 and 8, which are theoretical TOFs extrapolated to 1 M acid concentration.…”

Section: Electrocatalytic Production Of H2 With [Ni(p2n2)2]2+ Complexesmentioning

confidence: 99%

“…These three catalysts represent the current state of the art for H 2 production by the [Ni(P 2 N 2 ) 2 ] 2+ catalyst family and are recommended for benchmarking comparisons. Tafel plots for selected examples of other molecular catalysts are shown in Figure 30 for comparison, including the well-known 169 cobaloxime catalyst (4), 164 a highly active [Co 13 C 2 (CO) 24 ] 4− cluster complex (5), 165,166 synthetic model complexes of [FeFe]-hydrogenase (6) 167 and [NiFe]-hydrogenase (7), 167 and an Fe(porphyrin) complex (8). 168 Comparison of the TOF 0 values shows that the [Ni(P 2 N 2 ) 2 ] 2+ catalysts are more active than other molecular catalysts by two orders of magnitude or more.…”

Section: Molecular Tafel Plots For H 2 Productionmentioning

confidence: 99%

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Molecular Catalysts with Diphosphine Ligands Containing Pendant Amines

et al. 2022

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Pendant amines play an invaluable role in chemical reactivity, especially for molecular catalysts based on earth-abundant metals. As inspired by [FeFe]-hydrogenases, which contain a pendant amine positioned for cooperative bifunctionality, synthetic catalysts have been developed to emulate this multifunctionality through incorporation of a pendant amine in the second coordination sphere. Cyclic diphosphine ligands containing two amines serve as the basis for a class of catalysts that have been extensively studied and used to demonstrate the impact of a pendant base. These 1,5-diaza-3,7-diphosphacyclooctanes, now often referred to as “P2N2” ligands, have profound effects on the reactivity of many catalysts. The resulting [Ni(PR 2NR′ 2)2]2+ complexes are electrocatalysts for both the oxidation and production of H2. Achieving the optimal benefit of the pendant amine requires that it has suitable basicity and is properly positioned relative to the metal center. In addition to the catalytic efficacy demonstrated with [Ni(PR 2NR′ 2)2]2+ complexes for the oxidation and production of H2, catalysts with diphosphine ligands containing pendant amines have also been demonstrated for several metals for many different reactions, both in solution and immobilized on surfaces. The impact of pendant amines in catalyst design continues to expand.

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Section: Electrocatalytic Production Of H2 With [Ni(p2n2)2]2+ Complexesmentioning

confidence: 99%

Section: Molecular Tafel Plots For H 2 Productionmentioning

confidence: 99%

Molecular Catalysts with Diphosphine Ligands Containing Pendant Amines

et al. 2022

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“…This electron-sink behavior enables the application of metal carbonyl clusters in electrocatalytic processes . In particular, molecular Fe and Co carbonyl clusters have been employed as electrocatalysts for the two-electron reduction of two protons to molecular hydrogen and for the two-electron reduction of H + and CO 2 to formate. , The molecular nature of these clusters allows us to gain detailed structural insight into the electrocatalytic active species and into the overall mechanism occurring in the catalyst microenvironment . In this sense, the study of larger and larger molecular clusters such as HNMCCs represents an exciting frontier that could create a bridge to contemporary nanomaterials for electronic and electrochemical applications. − …”

Section: Introductionmentioning

confidence: 99%

Atomically Precise Ni–Pd Alloy Carbonyl Nanoclusters: Synthesis, Total Structure, Electrochemistry, Spectroelectrochemistry, and Electrochemical Impedance Spectroscopy

et al. 2021

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The molecular nanocluster [Ni 36– x Pd 5+ x (CO) 46 ] 6– ( x = 0.41) ( 1 6– ) was obtained from the reaction of [NMe 3 (CH 2 Ph)] 2 [Ni 6 (CO) 12 ] with 0.8 molar equivalent of [Pd(CH 3 CN) 4 ][BF 4 ] 2 in tetrahydrofuran (thf). In contrast, [Ni 37– x Pd 7+ x (CO) 48 ] 6– ( x = 0.69) ( 2 6– ) and [HNi 37– x Pd 7+ x (CO) 48 ] 5– ( x = 0.53) ( 3 5– ) were obtained from the reactions of [NBu 4 ] 2 [Ni 6 (CO) 12 ] with 0.9–1.0 molar equivalent of [Pd(CH 3 CN) 4 ][BF 4 ] 2 in thf. After workup, 3 5– was extracted in acetone, whereas 2 6– was soluble in CH 3 CN. The total structures of 1 6– , 2 6– , and 3 5– were determined with atomic precision by single-crystal X-ray diffraction. Their metal cores adopted cubic close packed structures and displayed both substitutional and compositional disorder, in light of the fact that some positions could be occupied by either Ni or Pd. The redox behavior of these new Ni–Pd molecular alloy nanoclusters was investigated by cyclic voltammetry and in situ infrared spectroelectrochemistry. All three compounds 1 6– , 2 6– , and 3 5– displayed several reversible redox processes and behaved as electron sinks and molecular nanocapacitors. Moreover, to gain insight into the factors that affect the current–potential profiles, cyclic voltammograms were recorded at both Pt and glassy carbon working electrodes and electrochemical impedance spectroscopy experiments performed for the first time on molecular carbonyl nanoclusters.

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“…We have previously demonstrated that the large metal carbonyl clusters promote hydride formation with rate 10 8 M –1 s –1 . − We believe that this fast rate has two possible origins. The multiple metal–metal bonds in the clusters serve as multiple sites for protonation, and this should provide a kinetic boost to the rate of cluster-hydride formation. , In addition, the high anionic charges, 3– or 4–, on the clusters promote PT: while the delocalized structures of the clusters enable access to modest reduction potentials relative to single-metal site electrocatalysts, at a given formal oxidation state or overall charge…”

Section: Introductionmentioning

confidence: 99%

Pre-Equilibrium Reaction Mechanism as a Strategy to Enhance Rate and Lower Overpotential in Electrocatalysis

Pattanayak

Berben

2023

J. Am. Chem. Soc.

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Pre-equilibrium reaction kinetics enable the overall rate of a catalytic reaction to be orders of magnitude faster than the ratedetermining step. Herein, we demonstrate how pre-equilibrium kinetics can be applied to breaking the linear free-energy relationship (LFER) for electrocatalysis, leading to rate enhancement 5 orders of magnitude and lowering of overpotential to approximately thermoneutral. This approach is applied to pre-equilibrium formation of a metal-hydride intermediate to achieve fast formate formation rates from CO 2 reduction without loss of selectivity (i.e., H 2 evolution). Fast preequilibrium metal-hydride formation, at 10 8 M −1 s −1 , boosts the CO 2 electroreduction to formate rate up to 296 s −1 . Compared with molecular catalysts that have similar overpotential, this rate is enhanced by 5 orders of magnitude. As an alternative comparison, overpotential is lowered by ∼50 mV compared to catalysts with a similar rate. The principles elucidated here to obtain pre-equilibrium reaction kinetics via catalyst design are general. Design and development that builds on these principles should be possible in both molecular homogeneous and heterogeneous electrocatalysis.

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Cobalt Carbonyl Clusters Enable Independent Control of Two Proton Transfer Rates in the Mechanism for Hydrogen Evolution

Cited by 12 publications

References 57 publications

Molecular Catalysts with Diphosphine Ligands Containing Pendant Amines

Molecular Catalysts with Diphosphine Ligands Containing Pendant Amines

Atomically Precise Ni–Pd Alloy Carbonyl Nanoclusters: Synthesis, Total Structure, Electrochemistry, Spectroelectrochemistry, and Electrochemical Impedance Spectroscopy

Pre-Equilibrium Reaction Mechanism as a Strategy to Enhance Rate and Lower Overpotential in Electrocatalysis

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