Small-angle X-ray scattering of carbon-supported Pt nanoparticles for fuel cell

Tsao, Cheng‐Si; Chen, C.-Y.

doi:10.1016/j.physb.2004.09.105

Cited by 12 publications

(6 citation statements)

References 12 publications

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“…Previous TEM and XRD studies on carbon-supported Pt nanoparticles also found that Pt/C distributions are best fit by a log-normal function. ,, The Pt scattering data were therefore fit using a log-normal distribution in the range 0.02 Å –1 < Q < 0.35 Å –1 , assuming the Pt particles are spheres, polydispersed, and scatter independently (i.e., approximated as a dilute system in Irena fitting). , This range of scattering vector ( Q ) corresponds to a diameter range of approximately 1.8–6.3 nm. The scattering intensity in this range results from primary platinum particles and not from cluster scattering …”

Section: Methodsmentioning

confidence: 93%

In Situ Anomalous Small-Angle X-ray Scattering Studies of Platinum Nanoparticle Fuel Cell Electrocatalyst Degradation

et al. 2012

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Polymer electrolyte fuel cells (PEFCs) are a promising high-efficiency energy conversion technology, but their cost-effective implementation, especially for automotive power, has been hindered by degradation of the electrochemically active surface area (ECA) of the Pt nanoparticle electrocatalysts. While numerous studies using ex situ post-mortem techniques have provided insight into the effect of operating conditions on ECA loss, the governing mechanisms and underlying processes are not fully understood. Toward the goal of elucidating the electrocatalyst degradation mechanisms, we have followed Pt nanoparticle growth during potential cycling of the electrocatalyst in an aqueous acidic environment using in situ anomalous small-angle X-ray scattering (ASAXS). ASAXS patterns were analyzed to obtain particle size distributions (PSDs) of the Pt nanoparticle electrocatalysts at periodic intervals during the potential cycling. Oxide coverages reached under the applied potential cycling protocols were both calculated and determined experimentally. Changes in the PSD, mean diameter, and geometric surface area identify the mechanism behind Pt nanoparticle coarsening in an aqueous environment. Over the first 80 potential cycles, the dominant Pt surface area loss mechanism when cycling to 1.0-1.1 V was found to be preferential dissolution or loss of the smallest particles with varying extents of reprecipitation of the dissolved species onto existing particles, resulting in particle growth, depending on potential profile. Correlation of ASAXS-determined particle growth with both calculated and voltammetrically determined oxide coverages demonstrates that the oxide coverage is playing a key role in the dissolution process and in the corresponding growth of the mean Pt nanoparticle size and loss of ECA. This understanding potentially reduces the complex changes in PSD and ECA resulting from various voltage profiles to a response dependent on oxide coverage.

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Section: Methodsmentioning

confidence: 93%

In Situ Anomalous Small-Angle X-ray Scattering Studies of Platinum Nanoparticle Fuel Cell Electrocatalyst Degradation

et al. 2012

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“…Knowledge about the structural features of the catalytic layer, understanding the distribution in this porous layer and understanding the proton mobility in PA between structural elements of the catalyst could help to design more efficient electrodes for fuel cells. While these materials have been studied microscopically 14, 15 there are only few works about nanoscale structure of the electrodes 16, 17, which described the structural features of the catalytic layer using small angle X‐ray scattering (SAXS). In the work of Stevens et al 17 the carbon/Pt is analyzed in terms of average diameter of the Pt particles.…”

Section: Introductionmentioning

confidence: 99%

Structure and Proton Dynamics in Catalytic Layer of HT‐PEFC

et al. 2016

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The present study focuses on structural and dynamical properties of the catalytic layer for high‐temperature polymer electrolyte fuel cells (HT‐PEFC). The catalytic layer is a composite material containing nanoporous carbon, poly(tetrafluoroethylene) (PTFE) and platinum (Pt) nanoparticles. The structure of the catalyst is investigated using small angle X‐ray scattering (SAXS) following different preparation steps of the electrodes: pure carbon support, platinum/carbon (Pt/C) powder and finally, complete catalytic layer. The structural properties of the Pt/C powder containing different amounts of Pt are discussed along with the size distribution of Pt particles and their arrangement on the surface of the carbon support. Following the preparation sequence of the catalytic layer based on the Pt/C powders the electrodes with different final Pt loadings are analyzed in details. Investigation of the structure of the catalytic layer is accompanied by the study of nanosecond dynamics of the phosphoric acid (PA) in the catalytic layer containing different amount of Pt by means of neutron backscattering spectroscopy. The structure of the catalytic layer is mostly determined by the structure of the catalytic powder and does not vary significantly with Pt loading in the electrode. The behavior of the PA is sensitive to the Pt content in the electrode.

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“…Tsao et al [19] investigated the structure of Pt NPs for DMFCs with high Pt mass loading and showed a 40% loss of the particles surface to volume ratio. SAXS can be performed with laboratory devices as well as employing synchro-tron light.…”

Section: Introductionmentioning

confidence: 99%

SAXS Analysis of Catalyst Degradation in High Temperature PEM Fuel Cells Subjected to Accelerated Ageing Tests

et al. 2014

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The loss in performance during fuel cell operation is one of the critical factors that hamper fuel cells commercialization. This paper presents a research activity related to high temperature polymer electrode membrane fuel cell (HT-PEMFC) degradation. The aim of the study is to investigate catalyst degradation of membrane electrode assemblies (MEAs) subjected to load cycles. Two HT-PEM MEAs have been subjected to accelerated ageing tests based on load cycling. The cycles profile has been chosen in order to enhance catalyst degradation. Both the tests show a fuel cell performance loss lower than 30mV after 100,000 cycles at 600mAcm–2. In order to analyze the catalyst evolution, synchrotron small angle X-ray scattering (SAXS) has been employed. The catalyst degradation of the two conditioned samples has been compared with the data obtained from a new MEA that has been used as reference sample. The SAXS results showed a mean size increase of the platinum nanoparticles up to the 100%

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Small-angle X-ray scattering of carbon-supported Pt nanoparticles for fuel cell

Cited by 12 publications

References 12 publications

In Situ Anomalous Small-Angle X-ray Scattering Studies of Platinum Nanoparticle Fuel Cell Electrocatalyst Degradation

In Situ Anomalous Small-Angle X-ray Scattering Studies of Platinum Nanoparticle Fuel Cell Electrocatalyst Degradation

Structure and Proton Dynamics in Catalytic Layer of HT‐PEFC

SAXS Analysis of Catalyst Degradation in High Temperature PEM Fuel Cells Subjected to Accelerated Ageing Tests

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