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Instruments / Technical Area	Publication Details	Published	Actions
B18-Core EXAFS	The dissolution dilemma for low Pt loading polymer electrolyte membrane fuel cell catalysts Daniel J. S. Sandbeck , Niklas Mørch Secher , Masanori Inaba , Jonathan Quinson , Jakob Ejler Sørensen , Jakob Kibsgaard , Alessandro Zana , Francesco Bizzotto , Florian D. Speck , Michael T. Y. Paul , Alexandra Dworzak , Carsten Dosche , Mehtap Oezaslan , Ib Chorkendorff , Matthias Arenz , Serhiy Cherevko Journal Of The Electrochemical Society 167 DOI: 10.1149/1945-7111/abc767 Diamond Proposal Number(s): [12746] Open Access Show Abstract ▼ Abstract: Cost and lifetime currently hinder widespread commercialization of polymer electrolyte membrane fuel cells (PEMFCs). Reduced electrode Pt loadings lower costs; however, the impact of metal loading (on the support) and its relation to degradation (lifetime) remain unclear. The limited research on these parameters stems from synthetic difficulties and lack of in situ analytics. This study addresses these challenges by synthesizing 2D and 3D Pt/C model catalyst systems via two precise routes and systematically varying the loading. Pt dissolution was monitored using on-line inductively coupled plasma mass spectrometry (on-line-ICP-MS), while X-ray spectroscopy techniques were applied to establish the oxidation states of Pt in correlation with metal loading. Dissolution trends emerge which can be explained by three particle proximity dependent mechanisms: (1) shifts in the Nernst dissolution potential, (2) redeposition, and (3) alteration of Pt oxidation states. These results identify engineering limitations, which should be considered by researchers in fuel cell development and related fields.	Dec 2020
B18-Core EXAFS	Investigating particle size effects in catalysis by applying a size controlled and surfactant-free synthesis of colloidal nanoparticles in alkaline ethylene glycol – the case study of the oxygen reduction reaction on Pt Jonathan Quinson , Masanori Inaba , Sarah Neumann , Andreas Abildgaard Swane , Jan Bucher , Søren Bredmose Simonsen , Luise Theil Kuhn , Jacob Judas Kain Kirkensgaard , Kirsten M. O. Jensen , Mehtap Oezaslan , Sebastian Kunz , Matthias Arenz Acs Catalysis DOI: 10.1021/acscatal.8b00694 Diamond Proposal Number(s): [12746] Show Abstract ▼ Abstract: Colloidal platinum nanoparticles are obtained via a surfactant-free polyol process in alkaline ethylene glycol. In this popular synthesis, ethylene glycol functions as solvent and reducing agent. The preparation procedure is known for its reproducibility to obtain 1-2 nm nanoparticles, but at the same time the controlled preparation of larger nanoparticles is challenging. A reliable size control without the use of surfactants is a fundamental yet missing achievement for systematic investigations. In this work it is demonstrated how the molar ratio between NaOH and the platinum precursor determines the final particle size and how this knowledge can be used to prepare and study in a systematic way supported catalysts with defined size and metal loading. Using small-angle X-ray scattering, transmission electron microscopy, infra-red spectroscopy, X-ray absorption spectroscopy, pair distribution function and electrochemical analysis it is shown that changing the NaOH/Pt molar ratio from 25 to 3, the Pt nanoparticle size is tuned from 1 to 5 nm. This size range is of interest for various catalytic applications, such as the oxygen reduction reaction (ORR). Supporting the nanoparticles onto a high surface area carbon, we demonstrate how the particle size effect can be studied keeping the catalyst loading constant, an important aspect that in previous studies could not be accomplished.	Jun 2018

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