Is Cu instability during the CO<inf>2</inf>reduction reaction governed by the applied potential or the local CO concentration?

Cu-based catalysts have shown structural instability during the electrochemical CO2reduction reaction (CO2RR). However, studies on monometallic Cu catalysts do not allow a nuanced differentiation between the contribution of the applied potential and the local concentration of CO as the reaction intermediate since both are inevitably linked. We first use bimetallic Ag-core/porous Cu-shell nanoparticles, which utilise nanoconfinement to generate high local CO concentrations at the Ag core at potentials at which the Cu shell is still inactive for the CO2RR. Usingoperandoliquid cell TEM in combination withex situTEM, we can unequivocally confirm that the local CO concentration is the main source for the Cu instability. The local CO concentration is then modulated by replacing the Ag-core with a Pd-core which further confirms the role of high local CO concentrations. Product quantification during CO2RR reveals an inherent trade-off between stability, selectivity and activity in both systems

Scanning electrochemical cell microscopy as a tool for the evaluation of electrocatalytic activity at the nanoscale

Im Rahmen dieser Arbeit wurde ein elektrochemisches Rasterzellmikroskop (SECCM) aufgebaut und dazu benutzt, die Aktivität von Elektrokatalysatoren zu untersuchen. Die Konzeption und die folgende Optimierung (inclusive Hardware, Software und Rauschisolierung) sind ausführlich beschrieben. Das SECCM wurde verwendet, um geringe Mengen an Katalysatorpartikel mit hoher Präzision auf den empfindlichen Membranen von Flüssigzellen-Transmissionselektronenspektroskopie (LC-TEM) Chips zu immobilisieren. Das eröffnet die Möglichkeit, LC-TEM in der Forschung von Elektrokatalysatoren zu benutzten. Mittels des SECCM wurde weiterhin die Aktivität von Katalysatornanopartikel für die Sauerstoffentwicklungsreaktion in alkalischer Lösung untersucht. Dabei wurde ein Os-Komplex als interner Standard eingesetzt, um die Potentialdrift zu berücksichtigen und die tatsächlich gemessene aktive Oberfläche zu bestimmen. Dadurch konnte die Aktivität einzelner Katalysatorpartikel ermittelt werden

Electromagnetic Modeling and Thermal Analysis of a Non-Axisymmetric System for Induction Brazing

The electromagnetic process happening between an induction brazing coil and the brazing assembly was studied and is described in the following pages. Using the tools of numerical analysis, we managed to achieve 3-D simulation of the process, which includes presentation of the magnetic field, thermal heat transfer, and time dependence. The results presented are considered for two of commonly used materials&mdash;copper and stainless steel in the shape of pipes. The induction brazing coil is a complex C-shape to match with the real industrial practices. The results obtained from the model are in accordance with the experimental results, as in both the model and the experiment, the required temperature was reached in about 6 s. It was found that during the brazing process, the inductance of the winding increases by about 4 nH and the resistance by 1.5 mΩ, which is important for the coordination of the power supply