Physical Modeling of the Proton Density in Nanopores of PEM Fuel Cell Catalyst Layers

Muzaffar, Tasleem; Kadyk, Thomas; Eikerling, Michael

doi:10.1016/j.electacta.2017.05.052

Cited by 18 publications

(6 citation statements)

References 64 publications

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“…Some hypothesize that there is a strong specific interaction between PFSA sulfonate groups and platinum and that this interaction drives PFSA adsorption to catalyst particles in inks. However, we do not see indications of this (due to low adsorption), counter to other experimental evidence that shows sulfonate adsorption to platinum surfaces. ,− This is rationalized because the platinum in those experiments was polarized (relative to the potential of zero charge − ), while ours is under no applied potential. Additionally, in the operando PFSA/platinum interaction studies, the platinum is likely in a metallic state; conversely, the platinum surfaces here (and found in inks) will have some native oxide coverage, which has been shown to impact PFSA behavior .…”

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confidence: 94%

Probing Ionomer Interactions with Electrocatalyst Particles in Solution

2021

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The interaction between ionomer (ion-conducting polymer) and catalyst particles in porous electrodes of electrochemical energy-conversion devices is a critical yet poorly understood phenomenon that controls device performance. This interaction stems from that in the electrode precursor inks, which also governs porous-electrode morphology during formation. In this letter, we probe the origin of this interaction in solution to unravel the ionomer/particle agglomeration process. Quartz-crystal microbalance studies detail ionomer adsorption (with a range of charge densities) to model surfaces under a variety of solvent environments, and isothermal-titration-calorimetry experiments extract thermodynamic binding information to platinum-and carbon-black nanoparticles. Results reveal that under the conditions tested, ionomer binding to platinum is similar to carbon, suggesting that adsorption to platinum-on-carbon catalyst particles in inks is likely dictated mostly by hydrophobic interactions with the carbon surface. Furthermore, water-rich solvents (relative to propanol) promote ionomer adsorption. Finally, ionomer dispersions change with time, yielding dynamic binding interactions.

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contrasting

confidence: 94%

Probing Ionomer Interactions with Electrocatalyst Particles in Solution

2021

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“…Recently, Eikerling et al reported a significantly enhanced proton concentration for pore geometries for which the total Debye length is greater than the pore width that further enhances conductivity. 76 In addition, the thickness and structure of the ionomer influences the oxygen permeation to the catalyst particles. 77 A reduction in Pt loading of the electrodes could decrease the fraction of hydrophilic surface area 78 and may influence the resulting ionomer structure and the electrode conductivity.…”

Section: Influence Of Fuel Cell Operation-thinning Of Ionomer Films-mentioning

confidence: 99%

High-Resolution Analysis of Ionomer Loss in Catalytic Layers after Operation

Morawietz

Handl

Oldani

et al. 2018

J. Electrochem. Soc.

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The function of catalytic layers in fuel cells and electrolyzers depends on the properties of the ionically conductive phase, which are most commonly perfluorinated ionomers based on Nafion and Aquivion. An analysis by atomic force microscopy reveals that the ultrathin ionomer films around Pt/C agglomerates have a thickness distribution ranging from 3.5 nm to 20 nm. Their conductivity and gas permeation properties determine the fuel cell performance to a large extend. For electrodes in Aquivion-based membraneelectrode-assemblies operation-induced structure changes were investigated by means of material-and conductivity-sensitive atomic force microscopy, infrared spectroscopy and electron-dispersive X-ray analysis. The observed thinning of the ultrathin ionomer films was mainly caused by polymer degradation deduced from reduced swelling after long-time operation and a significant loss of ionomer with operation time detected by infrared spectroscopy. From the linear thickness increase of the ultrathin films with rising humidity, a mainly layered structure of the ionomer was deduced. An influence of thickness of such ultrathin ionomer films on fuel cell lifetime was found by analysis of differently prepared membrane-electrode-assemblies, where a linear increase of irreversible degradation rate with ionomer film thickness in the electrodes of unused membrane-electrode-assemblies was found.

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“…Moreover, it predicts the impact of pH on the metal charging behaviour [73]. It was applied to rationalize electrochemical processes in a water-filled nanopore with Pt plated walls [75], the particle proximity effect in nanoparticle electrocatalysis [76], and induced charge effects by an ionomer skin layer in catalyst layers of PEM fuel cells [77]. In combination with microkinetic modeling and input of basic boundary layer and reaction parameters from electronic DFT, the model allowed the oxygen reduction reaction to be deciphered and effective electrode parameters to be calculated [78], as explained in Figure 4 The CHE has been the most versatile and successful computational approach to date.…”

Section: Accepted Manuscript 3 Theoretical Frameworkmentioning

confidence: 99%

Approaching the self-consistency challenge of electrocatalysis with theory and computation

Eslamibidgoli

Eikerling

2018

Current Opinion in Electrochemistry

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This is a PDF file of an unedited manuscript that has been accepted for publication. Highlights • In electrocatalysis, complex nonlinear and non-monotonic coupling arises in the boundary region between metal and electrolyte • A recent theoretical framework demonstrates how to handle this coupling • Approaches in first-principles electrochemical modeling need to be modified to consistently treat nonlinear and non-monotonic charging effects

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Physical Modeling of the Proton Density in Nanopores of PEM Fuel Cell Catalyst Layers

Cited by 18 publications

References 64 publications

Probing Ionomer Interactions with Electrocatalyst Particles in Solution

Probing Ionomer Interactions with Electrocatalyst Particles in Solution

High-Resolution Analysis of Ionomer Loss in Catalytic Layers after Operation

Approaching the self-consistency challenge of electrocatalysis with theory and computation

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