The role of adsorbed hydroxide in hydrogen evolution reaction kinetics on modified platinum

McCrum, Ian T.; Koper, Marc T. M.

doi:10.1038/s41560-020-00710-8

“…The superior activity of Ni-H2-NH3 is, thus, due its optimized HBE. While in some studies the OHBE is proposed to correlate with the activation barrier of Volmer step34 , and a decreasing OHBE is expected to decrease the HOR activity 24 , our thermodynamic characterizations and analysis indicate that in the present case the influence of HBE dominates. An understanding of the high activity of Ni-H2-NH3 in terms of factors beyond thermodynamics, for example, transition state barriers, interfacial electrical field, solvent dynamics,35 required further studies.…”

mentioning

confidence: 58%

An Efficient Nickel Hydrogen Oxidation Catalyst for Hydroxide Exchange Membrane Fuel Cells

Ni¹,

Wang²,

Héroguel³

et al. 2021

Preprint

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The hydroxide exchange membrane fuel cell (HEMFC) is a promising energy conversion technology, but it is limited by the need of platinum-group-metal (PGM) electrocatalysts, especially for the hydrogen oxidation reaction (HOR). Here we report a Ni-based HOR catalyst that exhibits an electrochemical surface area-normalized exchange current density of 70 μA/cm2, the highest among PGM-free catalysts. The catalyst comprises of Ni nanoparticles embedded in a nitrogen-doped carbon support. According to X-ray and ultraviolet photoelectron spectroscopy as well as H2 chemisorption, the electronic interaction between the Ni nanoparticles and its support leads to an optimal hydrogen binding energy, which is the likely origin of its high activity. PGM-free HEMFCs employing this Ni HOR catalyst give a peak power density of 450 mW/cm2, up to 6 times higher than previous best-performing analogous. This work demonstrates the feasibility of efficient PGM-free HEMFCs.<br>

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“…The superior activity of Ni-H2-NH3 is, thus, due its optimized HBE. While in some studies the OHBE is proposed to correlate with the activation barrier of Volmer step34 , and a decreasing OHBE is expected to decrease the HOR activity 24 , our thermodynamic characterizations and analysis indicate that in the present case the influence of HBE dominates. An understanding of the high activity of Ni-H2-NH3 in terms of factors beyond thermodynamics, for example, transition state barriers, interfacial electrical field, solvent dynamics,…”

mentioning

confidence: 58%

An Efficient Nickel Hydrogen Oxidation Catalyst for Hydroxide Exchange Membrane Fuel Cells

Ni¹,

Wang²,

Héroguel³

et al. 2021

Preprint

0

View full text Add to dashboard Cite

The hydroxide exchange membrane fuel cell (HEMFC) is a promising energy conversion technology, but it is limited by the need of platinum-group-metal (PGM) electrocatalysts, especially for the hydrogen oxidation reaction (HOR). Here we report a Ni-based HOR catalyst that exhibits an electrochemical surface area-normalized exchange current density of 70 μA/cm2, the highest among PGM-free catalysts. The catalyst comprises of Ni nanoparticles embedded in a nitrogen-doped carbon support. According to X-ray and ultraviolet photoelectron spectroscopy as well as H2 chemisorption, the electronic interaction between the Ni nanoparticles and its support leads to an optimal hydrogen binding energy, which is the likely origin of its high activity. PGM-free HEMFCs employing this Ni HOR catalyst give a peak power density of 450 mW/cm2, up to 6 times higher than previous best-performing analogous. This work demonstrates the feasibility of efficient PGM-free HEMFCs.<br>

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“…Indeed, the pH-dependence of electrocatalytic reactions has been and remains a subject of vigorous research. 45,39,46,47,48,49,50,51,52 In these studies, researchers have invoked pH-dependent adsorption energies 48,51 , electric eld strengths 45,50,52 , potentials of zero charge 45,49,50 , and water reorganization barriers 45 as contributions to the pH-dependence of a variety of half-reactions. Our studies imply that those same effects, with the additional contribution of varying mixed potentials, are relevant for thermochemical catalysis as well.…”

Section: Resultsmentioning

confidence: 99%

Thermochemical Aerobic Oxidation Catalysis in Water Proceeds via Coupled Electrochemical Half-Reactions

Ryu

¹

,

Bregante

²

,

Howland

³

et al. 2021

Preprint

0

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Heterogeneous aqueous-phase aerobic oxidations are an important emerging class of catalytic transformations, particularly for upgrading next generation bio-derived substrates. The mechanism of these reactions and the precise role of O2 in particular remains unclear. Herein, we test the hypothesis that thermochemical aerobic oxidation proceeds via two coupled electrochemical half-reactions for oxygen reduction and substrate oxidation. We collect electrochemical and thermochemical data on common noble metal catalysts under identical reaction/transport environments, and find that the electrochemical polarization curves of the O2 reduction and the substrate oxidation half-reaction closely predict the mixed potential of the catalyst measured in operando during thermochemical catalysis across 13 diverse variables spanning reaction conditions, catalyst composition, reactant identity, and pH. Additionally, we find that driving the oxidation half-reaction reaction electrochemically in the absence of O2 at the mixed potential leads to very similar rates and selectivities as for the thermochemical reaction in all cases examined. These findings strongly indicate that the role of O2 in thermochemical aerobic oxidation is solely as an electron scavenger that provides an incipient electrochemical driving force for substrate oxidation. These studies provide a quantitative and predictive link between thermochemical and electrochemical catalysis, thereby enabling the rational design of new thermochemical liquid-phase aerobic oxidation schemes by applying the principles of electrochemistry.

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The role of adsorbed hydroxide in hydrogen evolution reaction kinetics on modified platinum

Cited by 504 publications

References 54 publications

An Efficient Nickel Hydrogen Oxidation Catalyst for Hydroxide Exchange Membrane Fuel Cells

An Efficient Nickel Hydrogen Oxidation Catalyst for Hydroxide Exchange Membrane Fuel Cells

An Efficient Nickel Hydrogen Oxidation Catalyst for Hydroxide Exchange Membrane Fuel Cells

Thermochemical Aerobic Oxidation Catalysis in Water Proceeds via Coupled Electrochemical Half-Reactions

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