Reaction rate and separation factor isotope effects in the hydrogen evolution reaction

Salomon, Mark; Conway, B. E.

doi:10.1002/bbpc.19650690804

Cited by 16 publications

(12 citation statements)

References 44 publications

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“…This indicates that proton discharge on the Ni foam is the rate limiting step (i. e., the concentration of NiÀ H* species is significantly larger than that of NiÀ D* species). [40,[50][51][52] Further, that the H/D ratio of 84 : 16 is maintained at each olefinic carbon indicates that both H atoms are transferred to the alkyne from the Ni foam, ruling out involvement of protodemetallation steps in the mechanistic cycle (Scheme 4). The formation of vinyl radicals has been also discarded, as control experiments in the presence of radical scavengers did not affect the outcome of the reaction (Figure S10).…”

Section: Deuterated Arylacetylene Derivatives 2 D-[d]-2 Z-[d]mentioning

confidence: 99%

Electrochemical Proton Reduction over Nickel Foam for Z‐Stereoselective Semihydrogenation/deuteration of Functionalized Alkynes

et al. 2021

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Selective reduction strategies based on abundant-metal catalysts are very important in the production of chemicals. In this paper, a method for the electrochemical semihydrogenation and semideuteration of alkynes to form Z-alkenes was developed, using a simple nickel foam as catalyst and H 3 O + or D 3 O + as sources of hydrogen or deuterium. Good yields and excellent stereoselectivities (Z/E up to 20 : 1) were obtained under very mild reaction conditions. The reaction proceeded with terminal and nonterminal alkynes, and also with alkynes containing easily reducible functional groups, such as carbonyl groups, as well as aryl chlorides, bromides, and even iodides. The nickelfoam electrocatalyst could be recycled up to 14 times without any change in its catalytic properties.

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Section: Deuterated Arylacetylene Derivatives 2 D-[d]-2 Z-[d]mentioning

confidence: 99%

Electrochemical Proton Reduction over Nickel Foam for Z‐Stereoselective Semihydrogenation/deuteration of Functionalized Alkynes

et al. 2021

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“…Another way to study mechanism is through the kinetic isotope effect (KIE), particularly in organic and inorganic reactions. − Specifically, the substitution of hydrogen with deuterium many times yields large differences in reaction rates arising from reduced mass differences between the isotopes. , The use of KIE to study the ORR was pioneered by Yeager and co-workers. Their efforts show that Pt does not exhibit a KIE during ORR in phosphoric acid, signifying that the steps at or before the RDS do not involve protons .…”

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confidence: 99%

Elucidating Proton Involvement in the Rate-Determining Step for Pt/Pd-Based and Non-Precious-Metal Oxygen Reduction Reaction Catalysts Using the Kinetic Isotope Effect

Tse

Varnell

Hoang

et al. 2016

J. Phys. Chem. Lett.

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The development of non-precious-metal (NPM) catalysts to replace the Pt alloys currently used in fuel cells to facilitate the oxygen reduction reaction (ORR) is a vital step in the widespread utilization of fuel cells. Currently, the ORR mechanism for NPM catalysts is not well understood, prohibiting the design and preparation of improved NPM catalysts. We conducted a kinetic isotope effect (KIE) study to identify the rate-determining step (RDS) of this intricate electrocatalytic reaction involving multiple proton-coupled electron transfer (PCET) processes. We observed a KIE of about 2 for the ORR catalyzed by a NPM catalyst, which demonstrates that for these electrocatalysts protons are involved in the RDS during ORR. These results contribute to a more complete understanding of the ORR mechanism and suggest that the design of future NPM catalysts must include careful consideration of the role of protons during ORR.

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“…At applied potentials, more negative than −0.3 V, D + and H + are both reduced, forming D 2 , H 2 , and HD at the electrode surface. 30,31 It has been shown (by mass spectrometry analysis) 32 that the rates of their production are a function of the H + /D + concentrations; varying the ratio of H + /D + can be used to adjust the proportion of the gasses in the bubble.…”

Section: ■ Resultsmentioning

confidence: 99%

Electrochemical Generation of Individual Nanobubbles Comprising H₂, D₂, and HD

et al. 2020

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The electrochemical reduction of deuterons (2D + + 2e − → D 2 ) at Pt nanodisk electrodes (radius = 15−100 nm) in D 2 O solutions containing deuterium chloride (DCl) results in the formation of a single gas nanobubble at the electrode surface. Analogous to that previously observed for the electrochemical generation of H 2 nanobubbles, the nucleation and growth of a stable D 2 nanobubble is characterized in voltammetric experiments by a highly reproducible and well-resolved sudden drop in the faradaic current, a consequence of restricted mass transport of D + to the electrode surface following the liquid-to-gas phase transition. D 2 nanobubbles are stable under potential control due to a dynamic equilibrium existing between D 2 gas dissolution and electrochemical generation of D 2 at the circumference of the Pt nanodisk electrode. Remarkably, within the error of the experimental measurement (<6%), the electrochemical current required to nucleate a D 2 gas phase in a D 2 O solution is identical to that for the H 2 gas phase in a H 2 O solutions, indicating that the concentration required for nucleating a D 2 nanobubble in D 2 O (0.29 M) is ∼1.25 times larger than that for a H 2 nanobubble (0.23 M), while the supersaturation is ∼300 in each case. We further demonstrate that individual nanobubbles can be electrogenerated in mixed D 2 O/H 2 O solutions containing both D + and H + at respective individual concentrations well below those required to nucleate a gas phase containing either pure D 2 or H 2 . This latter finding indicates that the resulting nanobubbles comprise a mixture of D 2 , H 2 , and HD molecules with the chemical composition of a nanobubble determined by the concentrations and diffusivities of D + and H + in the mixed D 2 O/H 2 O solutions.

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Reaction rate and separation factor isotope effects in the hydrogen evolution reaction

Cited by 16 publications

References 44 publications

Electrochemical Proton Reduction over Nickel Foam for Z‐Stereoselective Semihydrogenation/deuteration of Functionalized Alkynes

Electrochemical Proton Reduction over Nickel Foam for Z‐Stereoselective Semihydrogenation/deuteration of Functionalized Alkynes

Elucidating Proton Involvement in the Rate-Determining Step for Pt/Pd-Based and Non-Precious-Metal Oxygen Reduction Reaction Catalysts Using the Kinetic Isotope Effect

Electrochemical Generation of Individual Nanobubbles Comprising H₂, D₂, and HD

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Reaction rate and separation factor isotope effects in the hydrogen evolution reaction

Cited by 16 publications

References 44 publications

Electrochemical Proton Reduction over Nickel Foam for Z‐Stereoselective Semihydrogenation/deuteration of Functionalized Alkynes

Electrochemical Proton Reduction over Nickel Foam for Z‐Stereoselective Semihydrogenation/deuteration of Functionalized Alkynes

Elucidating Proton Involvement in the Rate-Determining Step for Pt/Pd-Based and Non-Precious-Metal Oxygen Reduction Reaction Catalysts Using the Kinetic Isotope Effect

Electrochemical Generation of Individual Nanobubbles Comprising H2, D2, and HD

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Electrochemical Generation of Individual Nanobubbles Comprising H₂, D₂, and HD