Catalysis of Electron Transfer at Metal Electrodes

Santos, Elizabeth; Schmickler, Wolfgang

doi:10.1002/9780470929421.ch6

Cited by 15 publications

(25 citation statements)

References 28 publications

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“…Proton electrolyte fuel cells (PEFCs), a promising energy source, have attracted attention due to their high energy density, compactness, and low operating temperature. − In PEFCs, an oxygen reduction reaction (ORR) occurs on carbon-supported platinum (Pt/C) covered by proton-conducting perfluorosulfonated ionomers. Among these electrolyte materials, Nafion is the most widely used proton-conducting material in electrochemical systems due to its high proton conductivity and mechanical stability. , Since the ionomer/electrode interface plays a role in the electrochemical reaction field, controlling the morphology of the ionomer thin film on the Pt/C catalyst is directly related to ORR activity …”

Section: Introductionmentioning

confidence: 99%

Morphology Changes in Perfluorosulfonated Ionomer from Thickness and Thermal Treatment Conditions

et al. 2020

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The morphological changes of Nafion thin films with thicknesses from 10 to 200 nm on Pt substrate with various annealing histories (unannealed to 240 °C) were systematically investigated using grazing incidence small-angle X-ray scattering (GISAXS) and grazing incidence wide-angle X-ray scattering (GIWAXS). The results revealed that the hydrophilic ionic domain and hydrophobic backbone in Nafion thin films changed significantly when the annealing treatment exceeded the cluster transition temperature, which decreased proton conductivity, due to the constrained hydrophilic/hydrophobic phase separation, and increased the crystalline-rich domain. This research contributed to the understanding of ionomer thermal stability in the catalyst layer, which is subjected to thermal annealing during the hot-pressing process.

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Section: Introductionmentioning

confidence: 99%

Morphology Changes in Perfluorosulfonated Ionomer from Thickness and Thermal Treatment Conditions

et al. 2020

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“…For this reason, electrocatalysts are routinely employed to lower the energy barrier required for molecular hydrogen generation. HER on an electrocatalyst requires considerably lower overpotentials with respect to nonelectrocatalytic surfaces. − In general, noble metals are classical catalysts for HER, yielding optimal overpotentials . These materials are however also costly and rare, and these exact reasons induced researchers to investigate possible low-cost alternatives for both HER and OER. − Consequently, a wealth of electrocatalytic materials have been developed in the last few decades.…”

Section: Introductionmentioning

confidence: 99%

Nickel Phosphides Fabricated through a Codeposition–Annealing Technique as Low-Cost Electrocatalytic Layers for Efficient Hydrogen Evolution Reaction

Bernasconi

Khalil

Iaquinta

et al. 2020

ACS Appl. Energy Mater.

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Water splitting will be one of the most strategic techniques in the upcoming hydrogen-based economy. In this context, the development of efficient and low-cost Pt-free electrocatalysts is crucial to make it economically viable. The present work proposes a low-cost and scalable methodology to produce electrocatalytic layers based on nickel phosphide for hydrogen evolution reaction. In particular, a nickel–phosphorus solid solution is electrolytically codeposited together with red phosphorus particles. This approach overcomes the compositional limit typical of electrodeposited Ni–P by providing a supplementary phosphorous source directly embedded in the layer and makes it possible to synthesize high-P phosphides such as Ni12P5 and Ni2P. The obtained composites are subjected to different annealing cycles to precipitate phosphides, evidencing a major influence of process conditions on the final phase composition. X-ray photoelectron spectroscopy reveals the presence of a phosphorus-depleted region in correspondence of the surface of the samples. Finally, layers are tested to assess their electrocatalytic performances, and the effects of annealing time and catalyst loading are investigated. Samples with an optimized content of Ni2P evidence the lowest overpotential values, with 224 mV at 10 mA/cm2, and good stability over time.

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“…Subjecting a platinum electrode to oxidation–reduction cycles (ORCs) is one of the most commonly performed experiments in surface electrochemistry. This pretreatment cleans the platinum surface and results in a reproducible (albeit typically unknown) surface structure. − It is well-known that the Pt surface undergoes a significant structural transformation during this process, as is most dramatically illustrated when starting with a well-defined Pt(111) single crystal electrode . Understanding the roughening of a Pt(111) electrode by ORCs at the atomic scale has therefore been a long-standing goal in fundamental electrochemistry.…”

Section: Introductionmentioning

confidence: 99%

Atomic-Scale Identification of the Electrochemical Roughening of Platinum

2019

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Electrode degradation under oxidizing conditions is a major drawback for large-scale applications of platinum electrocatalysts. Subjecting Pt(111) to oxidation–reduction cycles is known to lead to the growth of nanoislands. We study this phenomenon using a combination of simultaneous in situ electrochemical scanning tunneling microscopy and cyclic voltammetry. Here, we present a detailed analysis of the formed islands, deriving the (evolution of the) average island growth shape. From the island shapes, we determine the densities of atomic-scale defect sites, e.g., steps and facets, which show an excellent correlation with the different voltammetric hydrogen adsorption peaks. Based on this combination of electrochemical scanning tunneling microscopy (EC-STM) and CV data, we derive a detailed atomistic picture of the nanoisland evolution during potential cycling, delivering new insights into the initial stages of platinum electrode degradation.

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Catalysis of Electron Transfer at Metal Electrodes

Cited by 15 publications

References 28 publications

Morphology Changes in Perfluorosulfonated Ionomer from Thickness and Thermal Treatment Conditions

Morphology Changes in Perfluorosulfonated Ionomer from Thickness and Thermal Treatment Conditions

Nickel Phosphides Fabricated through a Codeposition–Annealing Technique as Low-Cost Electrocatalytic Layers for Efficient Hydrogen Evolution Reaction

Atomic-Scale Identification of the Electrochemical Roughening of Platinum

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