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Successful year 2019!

23/01/2020 - New papers.

Year 2019 was successful for the group - 14 papers were published in prestigious peer-reviewed journals! Below is a highlight of 3 recent papers just published in the Journal of the Electrochemical Society and an invited issue of PhysChemPhys.

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Evaluating electrocatalysts at realistic current and potential ranges.

Article title: Evaluating Electrocatalysts at Relevant Currents in a Half-Cell: The Impact of Pt Loading on Oxygen Reduction Reaction

Authors: Konrad Ehelebe, Dominik Seeberger, Mike T. Y. Paul, Simon Thiele, Karl J. J. Mayrhofer and Serhiy Cherevko

The fundamental fuel cells electrocatalysis research relies on the so-called thin-film rotating disk electrode (TF-RDE) method. On the other hand, experiments on the single cell level is the daily routine in the applied research. Both have their pros and cons. In our work gas diffusion electrode (GDE) half-cells experiments are proposed as a powerful tool to bridge the gap between two extremes. We show that it is possible to transfer the advantages of TF-RDE such as good comparability of results, dedicated elimination of undesired parameters etc. to relevant potential and current ranges for fuel cell applications without inherent mass transport limitations.
With the developed setup and electrochemical protocol, first experiments on different Pt/C loadings confirm excellent reproducibility. Thereby mass-specific current densities up to 30 A mgPt-2 at 0.6 V vs. RHE are achieved. From a methodological perspective, good comparability to single cell measurements is obtained after theoretical corrections for temperature and concentration effects.
More details can be found online with open access in The Journal of Electrochemical Society - http://jes.ecsdl.org/content/166/16/F1259.full.pdf+html.

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Putting electrochemistry and mass spectrometry on the same time scale.

Article title: On the Time Resolution of Electrochemical Scanning Flow Cell Coupled to Downstream Analysis

Authors: Viacheslav Shkirskiy, Florian Dominik Speck, Nadiia Kulyk and Serhiy Cherevko

On-line downstream analysis using scanning flow cell (SFC) and ICP-MS has proven a powerful tool in electrocatalysis and corrosion science. It allows quantification of tiny amounts of materials dissolved in electrolyte. Moreover, it provides time- and potential-resolved analysis capabilities. Nevertheless, in this approach unambiguous correlation of the concentration of dissolved species vs. potential/current represents a significant challenge due to different time scales of electrochemical and concentration transients. Current paper addresses this challenge by finding a residence time distribution (RTD) of the SFC-ICP-MS. As an example, application of the obtained RTD to deconvolute experimental Pt dissolution profile (see figure) is shown. New finding is essential for mechanistic studies on Pt dissolution, which will follow. More details can be found online with open access - https://iopscience.iop.org/article/10.1149/2.1401915jes.

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Towards atomistic understanding of platinum dissolution.

Article title: Dissolution of Platinum Single Crystals in Acidic Medium

Authors: Daniel J. S. Sandbeck Dr. Olaf Brummel Prof. Dr. Karl J. J. Mayrhofer Prof. Dr. Jörg Libuda Dr. Ioannis Katsounaros Dr. Serhiy Cherevko

Modern fuel cells rely on platinum and platinum alloy electrocatalysts to catalyze both hydrogen oxidation and oxygen reduction reactions. During fuel cell operation, such catalysts can experience high anodic potentials, which will result in the dissolution of platinum. As an outcome of extensive experimental research performed over the last decade, including our on-line ICP-MS works, e.g. see our review (http://dx.doi.org/10.1016/j.nanoen.2016.03.005), dissolution of platinum on the macroscale has become well understood. On the other hand, atomistic understanding is still lacking. For this, in the study by Sandbeck et al., Pt single crystals were prepared and analyzed using on-line SFC-ICP-MS (see Figure showing CVs of different Pt single crystals). More details can be found online - https://doi.org/10.1002/cphc.201900866.

The current paper can be considered as one of the first Pt dissolution works required to understand how oxidation processes on the Pt surface lead to Pt leaving the lattice and result in the macroscopically observed dissolution. It quantifies Pt dissolution from different low indices Pt single crystals. Works have begun on bringing these results together with experimental data on Pt oxidation (surface synchrotron XRD, collaboration with Prof. Dr. Olaf Magnussen and Dr. Jakub Drnec) and theoretical mechanistic DFT studies on Pt extraction from the lattice (collaboration with Dr. Federico Calle-Vallejo). See updates on our homepage!

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