Non-destructive transmission electron microscopy study of catalyst degradation under electrochemical treatment

Mayrhofer, Karl Johann Jakob; Ashton, Sean; Meier, J.; Wiberg, Gustav K. H.; Hanzlik, Marianne; Arenz, Matthias

doi:10.1016/j.jpowsour.2008.08.003

Cited by 163 publications

(175 citation statements)

References 19 publications

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“…[14][15][16][17][18][19][20] Extended surface catalysts have also demonstrated durability benefits in the Pt sintering (0.6-0.9 V) and carbon corrosion (> 1.0 V) regimes, avoiding supports and Pt-carbon point contacts = These authors contributed equally to this work.…”

mentioning

confidence: 99%

“…[11][12][13] The advantages of extended surface catalyst over supported nanoparticle catalysts are still a matter of some debate, but have been attributed to a number of different factors, including the number of low coordinated sites (leading to higher specific activity and durability) and surface-enhanced proton conduction (which aids in ion accessibility and can reduce ionomer adsorption losses in activity). [14][15][16][17][18][19][20] Extended surface catalysts have also demonstrated durability benefits in the Pt sintering (0.6-0.9 V) and carbon corrosion (> 1.0 V) regimes, avoiding supports and Pt-carbon point contacts = These authors contributed equally to this work.…”

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confidence: 99%

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Fuel Cell Performance Implications of Membrane Electrode Assembly Fabrication with Platinum-Nickel Nanowire Catalysts

Mauger

Neyerlin

Alia

et al. 2018

J. Electrochem. Soc.

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Platinum-nickel nanowire (PtNiNW) catalysts have shown exceptionally high oxygen reduction mass activity in rotating disk electrode measurements. However, the ability to successfully incorporate PtNiNWs into high performance membrane electrode assemblies (MEAs) has been challenging due to their size, shape, density, dispersion characteristics, and corrosion-susceptible nickel core. We have investigated the impact of specific processing steps and electrode composition on observed fuel cell performance and electrochemical properties in order to optimize performance. We have found that nickel ion contamination is a major concern for PtNiNWs that can be addressed through ion exchange in fabricated/tested MEAs or by acid leaching of catalyst materials prior to MEA incorporation, with the latter being the more successful method. Additionally, decreased ionomer incorporation has led to the highest performance demonstrating 238 mA/mg Pt (0.9 V IR-free) for PtNiNWs (pre-leached to 80 wt% Pt) with 9 wt% ionomer incorporation. Platinum (and Pt alloy) nanoparticles on carbon supports (Pt/C) are the standard catalysts for polymer electrolyte fuel cells (PEMFCs). They are the basis for the thousands of fuel cell vehicles on the road today as well as tens of thousands of stationary polymer electrolyte fuel cell power systems. The performance of membrane electrode assemblies (MEAs) based on Pt/C has been optimized over multiple decades through tuning several parameters including carbon type, Pt to carbon loading, ionomer content/type, ink solvent composition, and coating/drying parameters.1-6 The implementation of unsupported metal catalysts in PEMFCs has seen much less investigation, and the application of non-Pt/C catalysts often falls back on the processes and compositions that have been optimized for Pt/C. For materials, like the nanowires presented here, it should not come as a surprise that dramatic differences in size/structure and properties (density, dispersability, magnetism, surface conductivity, ionomer interactions) significantly impact electrode performance and there is a need to investigate alternate, optimized fabrication compositions and approaches.To date, the motivation for the development and application of extended surface electrocatalysts in fuel cells has come largely from the promising work of 3M's nanostructured thin film (NSTF) materials. 7,8 These materials started as Pt thin films, but over the last several years have shifted to PtNi alloys, with much effort devoted to examining the sensitivity of activity to the alloy's composition.9,10 3M's NSTF is unique in that it is fabricated on a substrate and hot pressed directly into the membrane to form a MEA. Poly/single crystal studies of inherent catalytic activity and durability of flat metal surfaces further show significant benefits over nanoparticle catalysts consistent with findings of NSTF.11-13 The advantages of extended surface catalyst over supported nanoparticle catalysts are still a matter of some debate, but have been attributed to a number o...

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confidence: 99%

mentioning

confidence: 99%

Fuel Cell Performance Implications of Membrane Electrode Assembly Fabrication with Platinum-Nickel Nanowire Catalysts

Mauger

Neyerlin

Alia

et al. 2018

J. Electrochem. Soc.

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“…[39] An interesting family of EM methods relies on the Identical Location (IL) approach, a strategy devised to monitor the structural evolution of identical portions of the catalyst throughout the electrochemical accelerated degradation tests. Initially developed by Arenz and co-workers, [40] today it has become a common approach for several other groups. [39,41] It has been applied to several materials in a broad range of conditions and with different microscopy techniques, including (scanning) transmission electron microscopy ((S)TEM), scanning electron microscopy (SEM), and TEM-tomography.…”

Section: Degradation Of Supported Nanoparticles: Post-mortem Investigmentioning

confidence: 99%

Experimental Methodologies to Understand Degradation of Nanostructured Electrocatalysts for PEM Fuel Cells: Advances and Opportunities

et al. 2016

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The development and application of advanced experimental tools is a major driving force in modern electrocatalysis. This is particularly true for stability studies with nanostructured oxygen reduction reaction electrocatalysts for PEM fuel cells. Indeed, our understanding of the catalyst degradation mechanisms could not have been achieved without the arsenal of analytical tools developed over the last decades. This contribution aims at highlighting the value of such a multi-faceted analytical toolbox. Several classes are examined: from techniques applied for dissolution studies with bulk electrodes, to ex situ and in situ investigations with model high-surface-area catalysts. Finally, electrochemical and imaging methods employed to characterize catalyst layers are presented. The respective features, advantages, problems and possible future developments are discussed

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“…These results suggest that Pt dissolution, breakdown, migration and aggregation as well as carbon corrosion spread throughout the cathode electrocatalyst layer in the degraded MEA. It has been reported that Pt nanoparticles on carbon supports migrate with ease under the repeated durability testing conditions, resulting in dissolution, detachment, and agglomeration [81,82].…”

Section: Spatial Visualization Of a Cathode Pt/c Layer In Pefc Mea Bymentioning

confidence: 99%

Key Factors Affecting the Performance and Durability of Cathode Electrocatalysts in Polymer Electrolyte Fuel Cells Characterized by In Situ Real Time and Spatially Resolved XAFS Techniques

2014

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The account article treats with the characterizations of the structural and electronic transformations of Pt/C, Pt 3 Co/C, and Pt 3 Ni/C cathode electrocatalysts in polymer electrolyte fuel cells (PEFCs) involving Pt charging/discharging, Pt-O bond formation/breaking, and Pt-Pt bond breaking/reformation in cathode potential-jump processes and the rate constants of those transformations in the surface reaction sequences on the cathode electrocatalysts by in situ time-resolved X-ray absorption fine structure (XAFS) method. Spatially heterogeneous issue and mechanism for the Pt oxidation and degradation of Pt/C cathode electrocatalyst layers in PEFCs under the operating conditions, which should be uncovered for development of next-generation PEFCs, were also characterized by a scanning nano-XAFS mapping method and a laminography-XAFS method, respectively for 2D and 3D visualizations of Pt chemical species in Pt/C cathode electrocatalyst layers. These XAFS techniques provided new insights into critical issues affecting the performance and property of practical PEFCs under the operating conditions.

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Non-destructive transmission electron microscopy study of catalyst degradation under electrochemical treatment

Cited by 163 publications

References 19 publications

Fuel Cell Performance Implications of Membrane Electrode Assembly Fabrication with Platinum-Nickel Nanowire Catalysts

Fuel Cell Performance Implications of Membrane Electrode Assembly Fabrication with Platinum-Nickel Nanowire Catalysts

Experimental Methodologies to Understand Degradation of Nanostructured Electrocatalysts for PEM Fuel Cells: Advances and Opportunities

Key Factors Affecting the Performance and Durability of Cathode Electrocatalysts in Polymer Electrolyte Fuel Cells Characterized by In Situ Real Time and Spatially Resolved XAFS Techniques

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