<i>In Situ</i> Anomalous Small-Angle X-ray Scattering Investigation of Carbon-Supported Electrocatalysts

Haubold, H.‐G.; Wang, X. H.; Goerigk, G.; Schilling, W.

doi:10.1107/s0021889897002422

Cited by 62 publications

(72 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…14,[18][19][20][21][22] A comprehensive discussion of the ASAXS method and its use in characterizing carbon-supported metal catalysts can be found in several publications and textbooks. [23][24][25][26][27][28][29] One advantage this technique has is its ability to obtain element specific PSDs. From changes in the Pt and Cu PSDs obtained through ASAXS, Yu et al were able to show the in-situ formation of a Pt enriched shell surrounding a PtCu core through electrochemical Cu dissolution of a carbon supported Pt 25 Cu 75 electrocatalyst and Tuaev et al showed the same type of evolution for a Pt 25 Ni 75 electrocatalyst.…”

mentioning

confidence: 99%

In-Operando Anomalous Small-Angle X-Ray Scattering Investigation of Pt₃Co Catalyst Degradation in Aqueous and Fuel Cell Environments

Gilbert

Kropf

Kariuki

et al. 2015

J. Electrochem. Soc.

View full text Add to dashboard Cite

Platinum-cobalt alloy nanoparticles are of great interest as cathode catalysts for PEMFCs as they have been shown to have enhanced activity versus platinum. However, their relative stability against loss of electrochemically-active surface area in relation to Pt catalysts is still debated. In this study, the evolutions of Pt 3 Co particle size distributions (PSDs) in fuel cell and aqueous environments were followed during accelerated stress tests (ASTs) using in-operando ASAXS. The measured evolutions showed a degradation mechanism dominated by loss of particles smaller than the critical particle diameter (<5.2 to 6.1 nm, CPD), which depended on environment and the AST. These evolutions were compared to that of a Pt catalyst with a similar initial PSD, which was found to have a lower degradation rate than Pt 3 Co. The ASAXS data, as well as data from aqueous dissolution, X-ray absorption spectroscopy, individual particle energy-dispersive spectroscopy, X-ray fluorescence spectrometry, and kinetic Monte Carlo calculations support a loss mechanism of increased Pt dissolution from Pt 3 Co versus Pt due to destabilization caused by extensive dealloying of particles <∼5 nm during ASTs. Polymer electrolyte fuel cells (PEFCs) are a promising highefficiency energy conversion technology suitable for mobile and stationary applications. Two of the major issues still needing to be addressed for large-scale adoption are cost and durability. The major contributing factor to these issues is the electrocatalyst needed for the cathodic oxygen reduction reaction (ORR). Pt has been shown to be the best monometallic catalyst material for ORR 1 with high activity and good stability in the acidic environment of the PEFC.2,3 However, there is still a need for a more active, more stable, and less expensive cathode electrocatalyst to meet the demanding cost and lifetime requirements for many applications, especially for automotive propulsion power.Pt alloys are of great interest as ORR electrocatalysts as they are generally less expensive and have been shown to have enhanced activity versus Pt. [4][5][6] This enhancement in activity was found to be directly correlated with the Pt-Pt interatomic distance 7,8 and to the Pt d-band occupancy in the alloy. [8][9][10] However, there are concerns that the use of base metal alloying elements, which are generally less stable than Pt in acidic environments, could be accompanied by a loss in particle stability and corresponding loss in ORR activity. Conflicting reports exist about the overall stability of Pt alloy catalysts in relation to pure Pt catalysts. 5,6,[11][12][13] Some studies suggest that alloying has a positive effect while others show no significant impact on stability. It is known that relative stability is dependent on particle size, 14-16 the larger the initial particle size the more stable, and the majority of Pt alloy synthesis techniques are based on high temperature annealing processes which result in larger initial particle sizes. Therefore any comparisons between larger annea...

show abstract

mentioning

confidence: 99%

In-Operando Anomalous Small-Angle X-Ray Scattering Investigation of Pt₃Co Catalyst Degradation in Aqueous and Fuel Cell Environments

Gilbert

Kropf

Kariuki

et al. 2015

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

“…ASAXS can be applied to monitor the changes in average crystallite size (i.e., particle size in first approximation) and particle size distribution upon cycling, as shown by Gilbert et al [48] (Figure 6 c). Moreover, thanks to the high accuracy of ASAXS measurements, the size changes caused by the growth of an oxide layer [52] or the surface reconstruction caused by de-alloying can be probed. [53] The complementarity between electron microscopy, X-ray scattering and X-ray absorption spectroscopy methods as supporting tools to study the degradation of nanoparticles emerges clearly through these examples.…”

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

View full text Add to dashboard Cite

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

show abstract

“…The spacer lengths were calculated using the MNDO method. [45] The construction of the network structures is based on the assumption of the presence of an Alorganic monolayer on the particle surface, while the corresponding bond lengths were taken from the literature and the Cambridge Structural Database: (1) Al-Pt: 0.232 nm; [46] (2) Al-C: 0.187 nm; (3) Al-O: 0.232 nm. The thus-constructed Pt nanoparticles (1.2 nm) with the cross-linked spacers BDM and HPDB are illustrated in Figures 10 and 11, respectively.…”

Section: Modeling Of the Pt-spacer Interactionmentioning

confidence: 99%

Formation and Characterization of Pt Nanoparticle Networks

et al. 2005

View full text Add to dashboard Cite

Nanoparticle networks can be synthesized by the self‐assembly of arrays of metal colloid particles linked by spacer molecules of different sizes. The particles are linked through reactive aluminum sites in a metal–organic shell around the metal particles. Rigid spacer molecules with functional groups at each end are used to bind at these reactive sites. The resulting networks have been characterized by various methods such as transmission electron microscopy (TEM), sorption analysis, X‐ray absorption spectroscopy (XAFS), anomalous small angle X‐ray scattering (ASAXS), metastable impact electron spectroscopy (MIES), and ultraviolet photoelectron spectroscopy (UPS). These investigations showed that the metal nanoparticles form aggregated networks with average distances between the metal particles that are determined by the sizes of the spacer molecules applied. In this way, porous as well as nonporous networks have been obtained. Whether accessible pores are formed depends on the type of spacer molecule. Furthermore, the properties of the metal particles have proved to be sensitive towards the reaction of the aluminum in the protective shells with the linker molecules. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

show abstract

In Situ Anomalous Small-Angle X-ray Scattering Investigation of Carbon-Supported Electrocatalysts

Cited by 62 publications

References 1 publication

In-Operando Anomalous Small-Angle X-Ray Scattering Investigation of Pt₃Co Catalyst Degradation in Aqueous and Fuel Cell Environments

In-Operando Anomalous Small-Angle X-Ray Scattering Investigation of Pt₃Co Catalyst Degradation in Aqueous and Fuel Cell Environments

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

Formation and Characterization of Pt Nanoparticle Networks

Contact Info

Product

Resources

About

In Situ Anomalous Small-Angle X-ray Scattering Investigation of Carbon-Supported Electrocatalysts

Cited by 62 publications

References 1 publication

In-Operando Anomalous Small-Angle X-Ray Scattering Investigation of Pt3Co Catalyst Degradation in Aqueous and Fuel Cell Environments

In-Operando Anomalous Small-Angle X-Ray Scattering Investigation of Pt3Co Catalyst Degradation in Aqueous and Fuel Cell Environments

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

Formation and Characterization of Pt Nanoparticle Networks

Contact Info

Product

Resources

About

In-Operando Anomalous Small-Angle X-Ray Scattering Investigation of Pt₃Co Catalyst Degradation in Aqueous and Fuel Cell Environments

In-Operando Anomalous Small-Angle X-Ray Scattering Investigation of Pt₃Co Catalyst Degradation in Aqueous and Fuel Cell Environments