In-situ XAFS fuel cell measurements of a carbon-supported Pt–Ru anode electrocatalyst in hydrogen and direct methanol operation

Roth, Christina; Martz, Nathalie; Buhrmester, Thorsten; Scherer, Joachim; Fueß, H.

doi:10.1039/b204293b

Cited by 61 publications

(52 citation statements)

References 9 publications

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“…[10][11][12][13] Electrochemical cells for in situ X-ray spectroscopy studies of electrocatalysts have been published based on a PEFC-type design with a non-liquid polymer electrolyte. [14][15][16][17] Although for PEFC-related catalyst investigations such setups are advantageous, their use remains restricted to available polymer electrolytes. Especially for studies in alkaline environment, a cell design for liquid electrolytes is desirable.…”

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Electrochemical Flow-Cell Setup for In Situ X-ray Investigations

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et al. 2016

J. Electrochem. Soc.

109

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An electrochemical three-electrode flow-cell is presented for in situ small-angle X-ray scattering (SAXS) and X-ray absorption spectroscopy (XAS) experiments in transmission mode at synchrotron X-ray sources. The cell also allows for in situ XAS performed in fluorescence mode. Constant experimental conditions, even under moderate gas evolution, are provided by the electrolyte flow with controlled gas saturation. A special configuration of working and counter electrode, respectively, yields low residual ohmic resistance in three-electrode measurements that enables the study of thick porous electrodes of active high surface area materials. The cell proved its functionality and reliability in two studies: First, an in situ anomalous SAXS experiment for the high-potential degradation properties of a Pt/IrO 2 -TiO 2 catalyst for the oxygen reduction reaction at polymer electrolyte fuel cell cathodes; and second, an in situ XAS study of the electronic state of Ir centers inside an IrO 2 -TiO 2 catalyst under oxygen evolution conditions. © The Author Modern research in electrocatalysis makes extensive use of in situ X-ray techniques that provide information about the structure and the electronic state of catalyst materials under electrochemical potential control. The reason for this is the limited, merely indirect information about the state of the catalyst that can be deduced from purely electrochemical testing like cyclic voltammetry (CV) which often does not allow for an unambiguous interpretation of the data. In order to develop an understanding at a more fundamental level, additional information is required about the potential-dependent state of electrocatalyst materials that can be provided by synchrotron-based techniques like X-ray scattering or X-ray absorption spectroscopy.One example is the investigation of polymer electrolyte fuel cell (PEFC) Pt cathode catalyst degradation. Different mechanisms have been proposed for the loss of electrochemically active Pt surface area (ECSA) that occurs most severely at transient high-potential spikes during PEFC start and stop.1,2 Processes like agglomeration of primary Pt particles due to migration or carbon support corrosion, Pt loss due to dissolution, and growth of primary Pt nanoparticles due to dissolution/redeposition cycles have been considered 3,4 and quantified for different operation conditions and electrochemical environments. The most common technique applied for this purpose is transmission electron microscopy (TEM), which has the convenient advantage that changes of the Pt nanoparticle structure can be directly visualized, especially with the use of identical location TEM (IL-TEM).5 Although successfully demonstrated, 6 in situ TEM remains limited to certain electrochemical systems. Whereas the strength of TEM lies in the direct imaging of individual catalyst particles, it is challenging to extract quantitative statistical information about the entire catalyst sample from TEM analysis. Finally, the distinction of Pt nanoparticles from the support material p...

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confidence: 99%

Electrochemical Flow-Cell Setup for In Situ X-ray Investigations

Binninger

Fabbri

Pătru

et al. 2016

J. Electrochem. Soc.

109

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“…In the X-ray beam window region, a Pd counter electrode [41] was used in order to prevent perturbations of the electrical field on the catalyst under consideration [42,43]. Before XAS measurements, each new MEA was subjected to conditioning process at a voltage of~0.5 V for 15 min, and then Rapid Check cell performances by electrochemical cycles were done.…”

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Characterization of Nanomaterials in Electrochemistry

Greco¹

2015

Handbook of Nanoelectrochemistry

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Establishing new protocol for nanomaterial characterization of functional materials is an important step in our knowledge for understanding the correlation between atomic changes and electrochemical performances. We propose a combination of different state-of-the-art techniques as a robust approach for nanomaterial characterization, which is suitable in structural refinements of nanocrystalline active systems. This technique of studying microscopic properties of nanomaterials includes XAS (X-ray absorption spectroscopy) ex situ and in situ, XRD (X-ray diffraction), high-resolution TEM (transmission electron microscopy), and XRF (X-ray fluorescence). In particular, we are using the siteselective XAS (performed at international synchrotron radiation facilities) that is sensible to the local structure (up to 5-10 Å around photoabsorbing sites) for characterization of the nanomaterials with singular accuracy. An investigation of the local structure and chemical disorder dynamics of a commercial Pt-Co alloy nanocatalyst, used as electrode material in proton exchange membrane fuel cells (PEMFC), will be presented and discussed.

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“…[15±17] In particular X-ray absorption spectroscopy (XAS) is extremely suitable for in-situ experiments, as it is highly versatile, and measurements can be carried out in different environments, different atmospheres and at various temperatures. [15] The feasibility of in-situ V-ray absorption measurements in a working fuel cell has been shown by Viswanathan et al, [18,19] and by our group [20] both in 2002. The experimental set-up and in-situ cell of the Smotkin group, however, were somewhat different from those developed by our group, which have been tested successfully at the beamlines BM 29 at ESRF, Grenoble, and V 1 at Hasylab, Hamburg, as described in.…”

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“…The experimental set-up and in-situ cell of the Smotkin group, however, were somewhat different from those developed by our group, which have been tested successfully at the beamlines BM 29 at ESRF, Grenoble, and V 1 at Hasylab, Hamburg, as described in. [20] In the work presented here, the development and optimization of an in-situ XAS fuel cell in transmission and fluorescence geometry is reported. Different carbon-supported and unsupported Pt-Ru electrocatalysts were investigated, and spectra recorded at the Pt L 3 -and the Ru K-edge in the working fuel cell.…”

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Development of an In‐Situ Cell for X‐ray Absorption Measurements During Fuel Cell Operation

et al. 2005

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Low-temperature polymer electrolyte fuel cells (PEMFCs) are among the key technologies for future energy policies, as they offer an almost emission-free alternative to conventional energy sources and converters. [1] The main advantage of the fuel cell is the generation of electricity from hydrogen in an environmentally-friendly way without combustion, high temperatures, rotating parts and electrical generators. At present, the main drawback, however, is the high cost of the fuel cell technology, [2] and further research is required before fuel cells can compete with conventional energy sources in terms of cost efficiency and long-term performance.As long as pure hydrogen is used in the PEMFC, platinum is the most efficient catalyst at both the anode and the cathode side. For cost efficiency, however, it is intended to replace expensive pure hydrogen by methanol (direct methanol fuel cell ± DMFC) or reformate. In this case, the cell performance decreases considerably, since CO impurities from the fuel adsorb strongly on Pt surfaces poisoning the electrocatalytically active sites. [3] Consequently, one emphasis in fuel cell research is the development of less CO-sensitive catalysts. Over the past years different binary and ternary Pt systems, e.g. PtRu, [4±8] Pt-Mo, [9] Pt-Sn [10] and Pt-Ru-W, [11,12] were investigated and showed improved activity for the oxidation of H 2 /CO mixtures. However, in most cases the long-term stability of these catalysts has not been studied in detail. Recent investigations reported a significant drop in activity, apparently because many alloy catalysts are not stable under the acidic fuel cell working conditions. Often a fraction of the less-noble element, like non-alloyed Ru in Pt-Ru or especially Sn in Pt-Sn alloys, shows a tendency towards leaching into the electrolyte. In this background in-situ investigations seem indispensable to reveal and pursue structural changes of the catalyst during fuel cell operation.There are many different characterization methods that can be applied for in-situ investigations, e.g. in-situ FTIR, [13] V-ray diffraction, [14] and V-ray absorption spectroscopy. [15±17] In particular X-ray absorption spectroscopy (XAS) is extremely suitable for in-situ experiments, as it is highly versatile, and measurements can be carried out in different environments, different atmospheres and at various temperatures. [15] The feasibility of in-situ V-ray absorption measurements in a working fuel cell has been shown by Viswanathan et al., [18,19] and by our group [20] both in 2002. The experimental set-up and in-situ cell of the Smotkin group, however, were somewhat different from those developed by our group, which have been tested successfully at the beamlines BM 29 at ESRF, Grenoble, and V 1 at Hasylab, Hamburg, as described in. [20] In the work presented here, the development and optimization of an in-situ XAS fuel cell in transmission and fluorescence geometry is reported. Different carbon-supported and unsupported Pt-Ru electrocatalysts were investigated, ...

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In-situ XAFS fuel cell measurements of a carbon-supported Pt–Ru anode electrocatalyst in hydrogen and direct methanol operation

Cited by 61 publications

References 9 publications

Electrochemical Flow-Cell Setup for In Situ X-ray Investigations

Electrochemical Flow-Cell Setup for In Situ X-ray Investigations

Characterization of Nanomaterials in Electrochemistry

Development of an In‐Situ Cell for X‐ray Absorption Measurements During Fuel Cell Operation

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