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Es wird eine universelle, auf Nanokapillaren basierende Methode zur Probenabscheidung auf der Siliziumnitridmembran von LCTEM‐Chips (liquid cell transmission electron microscopy) vorgeschlagen. Sie ist auf alle Substanzen anwendbar, die in einem Lösungsmittel dispergierbar und für eine Tropfenimmobilisierung geeignet sind, einschließlich Katalysatoren, biologische Proben und Polymere. Am wichtigsten ist, dass diese Methode die Einschränkungen bezüglich der Probenimmobilisierung aufgrund der Zerbrechlichkeit der ultradünnen Glaskohlenstoffelektrode/Siliziumnitridmembran, die für die Elektronenübertragung erforderlich ist, überwindet. Somit wird ein einfacher Weg vorgestellt, um das Forschungsgebiet des LCTEM auf jede Probe zu erweitern, die zuvor extern abgeschieden werden kann. Mit dieser Methode werden NixB‐Nanopartikel auf der Arbeitselektrode des LCTEM‐Chips im μm‐Maßstab deponiert und die In‐situ‐Beobachtung einzelner Katalysatorpartikel während der Ethanoloxidation erstmals erfolgreich mithilfe von TEM‐Filmen durchgeführt. [ABSTRACT FROM AUTHOR]

A universal nano‐capillary based method for sample deposition on the silicon nitride membrane of liquid‐cell transmission electron microscopy (LCTEM) chips is demonstrated. It is applicable to all substances which can be dispersed in a solvent and are suitable for drop casting, including catalysts, biological samples, and polymers. Most importantly, this method overcomes limitations concerning sample immobilization due to the fragility of the ultra‐thin silicon nitride membrane required for electron transmission. Thus, a straightforward way is presented to widen the research area of LCTEM to encompass any sample which can be externally deposited beforehand. Using this method, NixB nanoparticles are deposited on the μm‐scale working electrode of the LCTEM chip and in situ observation of single catalyst particles during ethanol oxidation is for the first time successfully monitored by means of TEM movies. [ABSTRACT FROM AUTHOR]

Silicon clathrates have attracted interest as potential anodes for lithium‐ion batteries with unique framework structures. However, very little is known about the surface reactivity and solid electrolyte interphase (SEI) properties of clathrates. In this study, operando scanning electrochemical microscopy (SECM) is used to investigate the effect of pre‐treatment on the formation dynamics and intrinsic properties of the SEI in electrodes prepared from type I Ba8Al16Si30 silicon clathrates. Although X‐ray photoelectron spectroscopy (XPS) analysis does not reveal large changes in SEI composition, it is found through SECM measurements that ball‐milling combined with chemical acid/base etching of the clathrates lead to a more stable and rapidly formed SEI as compared to purely ball‐milled samples, resulting in enhanced coulombic efficiency. [ABSTRACT FROM AUTHOR]

Einzelpartikel‐Messungen ("single entity") sind essentiell für das Verständnis von Nanopartikel‐Elektrokatalysatoren, ohne Limitierung durch Stofftransport und lokale Änderungen der Eduktkonzentration oder des pH‐Wertes. Wir berichten über die elektrochemische Rasterzellmikroskopie (SECCM) an Kompositpartikeln aus Co/N‐dotiertem Kohlenstoff, abgeleitet aus ZIF‐67, hinsichtlich der Sauerstoffentwicklungsreaktion (OER). Um die inhärenten SECCM Schwierigkeiten der Oberflächenbenetzung in alkalischer Lösung sowie des Potentialdrifts zu überwinden, wurde ein nicht störender Os‐Komplex als frei diffundierender interner Potentialstandard verwendet. Die ermittelte Turnover‐Frequenz (TOF) beträgt 0,25 bis 1,5 s−1 bei Potentialen zwischen 1,7 und 1,8 V vs. RHE und korreliert mit der Anzahl der Co‐Atome in jedem Partikel. Konstante Werte an Orten mit unterschiedlicher Partikelanzahl belegen die OER‐Aktivität ohne den Einfluss makroskopischer Filmeffekte. [ABSTRACT FROM AUTHOR]

"Single entity" measurements are central for an improved understanding of the function of nanoparticle‐based electrocatalysts without interference arising from mass transfer limitations and local changes of educt concentration or the pH value. We report a scanning electrochemical cell microscopy (SECCM) investigation of zeolitic imidazolate framework (ZIF‐67)‐derived Co−N‐doped C composite particles with respect to the oxygen evolution reaction (OER). Surmounting the surface wetting issues as well as the potential drift through the use of a non‐interfering Os complex as free‐diffusing internal redox potential standard, SECCM could be successfully applied in alkaline media. SECCM mapping reveals activity differences relative to the number of particles in the wetted area of the droplet landing zone. The turnover frequency (TOF) is 0.25 to 1.5 s−1 at potentials between 1.7 and 1.8 V vs. RHE, respectively, based on the number of Co atoms in each particle. Consistent values at locations with varying number of particles demonstrates OER performance devoid of macroscopic film effects. [ABSTRACT FROM AUTHOR]

The selectivity of the chlorine evolution reaction over the oxygen evolution reaction during the electrolysis of aqueous NaCl is, despite being very high, still insufficient to prevent expensive separation of the formed Cl2 and O2 by means of liquefaction. We hypothesize that, by decreasing the local activity of H2O near the anode surface by substantially increasing the ionic strength of the electrolyte, the oxygen evolution reaction would be suppressed, leading concomitantly to a higher selectivity of Cl2 over O2 formation. Hence, the influence of the ionic strength on the competition between electrochemical evolution of O2 and Cl2 at dimensionally stable anodes (DSAs) was investigated. Addition of a high concentration of NaNO3, an inert electrolyte additive, increases the selectivity for chlorine at high current density, as determined by means of online electrochemical mass spectrometry and UV‐vis spectroscopy. We propose conditions in which free water is suppressed, owing to under‐coordination of the solvation shells of ions, as a general concept to modulate the selectivity of competing electrochemical reactions. [ABSTRACT FROM AUTHOR]

The reproducible fabrication of nanometre‐sized carbon electrodes poses great challenges. Especially, the field of single entity electrochemistry has strict requirements regarding the geometry of these electrochemical probes. Herein, an automated setup for the fabrication of carbon nanoelectrodes based on the pyrolysis of a propane/butane gas mixture within pulled quartz capillaries by means of a moving heating coil is presented. It is shown that mere electrochemical characterisation with conventional redox mediators does not allow for a reliable assessment of the electrode's geometry and quality. Therefore, high‐throughput transmission electron microscopy is used in parallel to evaluate and optimise preparation parameters. Control of the latter gives access to three different electrode types: nanopipettes, nanosamplers and nanodisks. Automated fabrication on the nano scale: an automated setup for the fabrication of carbon nanoelectrodes based on the pyrolysis within pulled quartz capillaries by means of a moving heating coil is presented. High‐throughput transmission electron microscopy is used to evaluate and optimise preparation parameters. Control gives access to three different electrode types: nanopipettes, nanosamplers and nanodisks. [ABSTRACT FROM AUTHOR]

Abstract: Local ion activity changes in close proximity to the surface of an oxygen depolarized cathode (ODC) were measured by scanning electrochemical microscopy (SECM). While the operating ODC produces OH− ions and consumes O2 and H2O through the electrocatalytic oxygen reduction reaction (ORR), local changes in the activity of OH− ions and H2O are detected by means of a positioned Pt microelectrode serving as an SECM tip. Sensing at the Pt tip is based on the pH‐dependent reduction of PtO and obviates the need for prior electrode modification steps. It can be used to evaluate the coordination numbers of OH− ions and H2O, and the method was exploited as a novel approach of catalyst activity assessment. We show that the electrochemical reaction on highly active catalysts can have a drastic influence on the reaction environment. [ABSTRACT FROM AUTHOR]

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Abstract: In order to design more powerful electrocatalysts, developing our understanding of the role of the surface structure and composition of widely abundant bulk materials is crucial. This is particularly true in the search for alternative hydrogen evolution reaction (HER) catalysts to replace platinum. We report scanning electrochemical cell microscopy (SECCM) measurements of the (111)‐crystal planes of Fe4.5Ni4.5S8, a highly active HER catalyst. In combination with structural characterization methods, we show that this technique can reveal differences in activity arising from even the slightest compositional changes. By probing electrochemical properties at the nanoscale, in conjunction with complementary structural information, novel design principles are revealed for application to rational material synthesis. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)