Youngmi Yi

N-heterocyclic carbene-silver complex as a novel reference electrode in electrochemical applications

We demonstrate a novel reference electrode material namely an organometallic silver complex e.g., silver (I) tetramethylbis(benzimidazolium) diiodide [1a] for both acid and alkaline electrolysis. The potential usage of the silver complex as a reference electrode with at least equal electrochemical capabilities compared to those of the conventional electrode materials (e.g., Hg/HgO in alkaline media and Ag/AgCl in acidic media) are also demonstrated using cyclic voltammetry. In addition, the well dispersed surface morphology and fine crystalinity of the silver complex is investigated using field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD).

Atomic scale insight on the increased stability of tungsten modified platinum/carbon fuel cell catalysts

The limited stability of carbon‐supported Pt catalysts for the oxygen reduction reaction is a key obstacle for their commercial application in fuel cells. Here we report on the properties of a tungsten‐modified Pt/C catalyst that shows enhanced stability under potential cycling conditions compared to a reference Pt/C catalyst. Although routine structural investigation by XRD and TEM show an inhomogeneous distribution of tungsten species on the modified catalyst surface, X‐ray photoelectron spectroscopy points to an overall changed catalytic behavior of Pt nanoparticles. Aberration‐corrected atomic‐scale imaging reveals the presence of homogeneously dispersed tungsten atomic species that decorate the surface of the carbon support and the Pt nanoparticles. The presented results demonstrate that detailed and localized imaging at the atomic scale is essential for the identification of the relevant species amongst spectator phases and thus, for the understanding of the improved integral behavior of a modified catalyst.

MAXNET Energy – Focusing Research in Chemical Energy Conversion on the Electrocatlytic Oxygen Evolution

Abstract MAXNET Energy is an initiative of the Max Planck society in which eight Max Planck institutes and two external partner institutions form a research consortium aiming at a deeper understanding of the electrocatalytic conversion of small molecules. We give an overview of the activities within the MAXNET Energy research consortium. The main focus of research is the electrocatalytic water splitting reaction with an emphasis on the anodic oxygen evolution reaction (OER). Activities span a broad range from creation of novel catalysts by means of chemical or material synthesis, characterization and analysis applying innovative electrochemical techniques, atomistic simulations of state-of-the-art x-ray spectroscopy up to model-based systems analysis of coupled reaction and transport mechanisms. Synergy between the partners in the consortium is generated by two modes of cooperation – one in which instrumentation, techniques and expertise are shared, and one in which common standard materials and test protocols are used jointly for optimal comparability of results and to direct further development. We outline the special structure of the research consortium, give an overview of its members and their expertise and review recent scientific achievements in materials science as well as chemical and physical analysis and techniques. Due to the extreme conditions a catalyst has to endure in the OER, a central requirement for a good oxygen evolution catalyst is not only its activity, but even more so its high stability. Hence, besides detailed degradation studies, a central feature of MAXNET Energy is a standardized test setup/protocol for catalyst stability, which we propose in this contribution.

In Situ Electrochemical Cells to Study the Oxygen Evolution Reaction by Near Ambient Pressure X-ray Photoelectron Spectroscopy

In this contribution, we report the development of in situ electrochemical cells based on proton exchange membranes suitable for studying interfacial structural dynamics of energy materials under operation by near ambient pressure X-ray photoelectron spectroscopy. We will present both the first design of a batch-type two-electrode cell prototype and the improvements attained with a continuous flow three-electrode cell. Examples of both sputtered metal films and carbon-supported metal nanostructures are included demonstrating the high flexibility of the cells to study energy materials. Our immediate focus was on the study of the oxygen evolution reaction, however, the methods described herein can be broadly applied to reactions relevant in energy conversion and storage devices.