The research interests of the research department “Electrocatalysis” are on electrochemical reactions that occur at solid-liquid interfaces and are relevant to electrochemical energy conversion (fuel cells, water or CO2 electrolyzers etc). Reactions of interest are: oxygen evolution, oxygen reduction, carbon dioxide reduction and others. Our focus is placed on finding active, selective and stable electrode materials for such reactions and thereafter the integration to real systems.
We develop innovative tools for the on-line monitoring of electrochemical reactions, by coupling sophisticated electrochemical cells (e.g. the scanning flow cell) with highly sensitive analytical techniques like ICP-MS or QMS. These unique tools enable the high-throughput investigation of a wide range of materials (material libraries) at an extremely short time, thereby accelerating material discovery. In addition, they allow obtaining fundamental insight on reaction mechanisms, which is essential to understand underlying processes. Promising solutions are thereafter tested in more applied electrochemical reactors, to evaluate the efficiency of processes and feasibility for real applications. The development of new methods for fundamental and applied investigations in electrocatalysis is a central activity at the ”Electrocatalysis“ research department.
Advanced electrochemical analytical tools - the Scanning Flow Cell (SFC)
The SFC is a home-made, advanced microelectrochemical flow cell which provides spatially-resolved information. The electrolyte is continuously flowing through the channels of the SFC over the catalyst, which is placed externally on a three-dimensional translation stage. The translation stage allows the fast and accurate positioning of the flow cell on one catalyst location only, thus other locations remain unaffected. The spatial resolution offered by the SFC allows the investigation of material libraries in a very short time. Thus, it is possible to understand relationships between catalyst composition and performance with addressing only a single with gradient composition. When homogeneous catalysts are used, the investigation of the operational parameters is possible, without the need to prepare the catalyst in every experiment, which offers excellent reproducibility. However, the electrochemical signal alone (e.g. current versus potential) does not provide information on, for instance, the dissolution products during catalyst degradation, or the product distribution in a complex electrochemical reaction that forms many products. This is solved by coupling the SFC with appropriate analytical techniques (e.g. real-time TOF/MS, ICP/MS, UV/Vis etc). This comprises a very powerful tool in which electrochemical data are complemented with information on the product distribution or elemental dissolution online. Therefore, the SFC allows the systematic investigation of an immeasurable number of materials and experimental conditions, at a time that is not accessible with state-of-the-art approaches.
X-ray Photoelectron Spectroscopy (XPS)
The Quantera II is a unique scanning XPS microprobe that provides outstanding large area and unequaled micro-area spectroscopy performance. It is designed for rapid, spatially resolved elemental and chemical analysis of solid surfaces.
Capabilities of the Quantera II include: x-ray beam induced secondary electron imaging for rapid and confident location of small sample features, large and micro-area spectroscopy, chemical state XPS imaging, high performance sputter depth profiling, automated angle dependent depth profiling, turnkey insulator analysis, and a robotic sample handling platform to automate the analysis of multiple experiments or samples.
The Quantera II provides x-ray excited secondary electron imaging of the sample surface in a manor analogous to how an SEM generates a secondary electron image. This unique feature utilizes the scanned x-ray beam to generate secondary electrons that are collected by the Quantera’s energy analyzer to provide images with topographical or surface chemical contrast information in a few seconds. X-ray excited secondary electron images can be acquired from insulating or conducting samples without coating or masking the sample. The use of the same hardware for secondary electron imaging and XPS measurements ensures that spectroscopic information is coming from areas selected on secondary electron images.
The Quantera II accepts up to three 75 x 75 mm sample platens that can be loaded with samples for automated analysis. The maximum sample size is 100 mm in diameter and up to 25 mm in thickness. Up to three platens may be loaded into the analysis chamber for automated analysis.
Focused Ion Beam - Scanning Electron Microscope (FIB-SEM)
For the characterization and machining of materials on the nanoscale, the HI ERN has installed a Zeiss XB 540. This microscope combines a scanning electron microscope (SEM) with a focussed ion beam (FIB). In this type of instrument, the electron beam is commonly used for imaging, while the ion beam serves the purpose of removal of very small volumes of material. For imaging, a number of detectors are present on the instrument, including for secondary electrons, backscattered electrons and transmitted electrons as well as electron backscatter diffraction (EBSD) and x-ray analysis (EDXS). For advanced sample manipulation and electrical probing, two micromanipulators with rotary axes and a micro-gripper are available. For beam sensitive samples, as well as samples containing components with a high vapour pressure at room temperature, a cryo-stage capable of cooling to -185°C is installed. To ensure optimal adoption to specific needs, software for automated sample preparation, tomography and hardware integration is available.
We additionally utilize standard electrochemical cells (e.g. 3-electrode RDE cells and 2-electrode electrolyzers), analytical setups (e.g. gas chromatographs, quadrupole mass spectrometers) or surface characterization techniques (SEM/EDX, XRF, Laser Scanning Microscope) etc.
- Importance and Challenges of Electrochemical in Situ Liquid Cell Electron Microscopy for Energy Conversion Research, Accounts of Chemical Research 49, 2016, 2015-2022.
- Durability of platinum-based fuel cell electrocatalysts: Dissolution of bulk and nanoscale platinum, Nano Energy 26, 2016, 275-298.
- Platinum recycling going green via induced surface potential alteration enabling fast and efficient dissolution, Nature Communications 7, 2016, 13164.
- Stability of dealloyed porous Pt/Ni nanoparticles, ACS Catalysis 5, 2015, 5000-5007.
- Oxygen electrochemistry as a cornerstone for sustainable energy conversion, Angewandte Chemie International Edition 53, 2014, 102-121.
- Dissolution of noble metals during oxygen evolution in acidic media, ChemCatChem 6, 2014, 2219-2223.
- Dissolution of platinum: limits for the deployment of electrochemical energy conversion?, Angewandte Chemie International Edition 51, 2012, 12613-12615.
Monolayer black phosphorus by sequential wet-chemical surface oxidation
RSC Advances 9(7), 3570 - 3576 (2019) [10.1039/C8RA09069F] Files Fulltext by OpenAccess repository BibTeX | EndNote: XML, Text | RIS
Impact of Palladium Loading and Interparticle Distance on the Selectivity for the Oxygen Reduction Reaction toward Hydrogen Peroxide
The journal of physical chemistry <Washington, DC> / C C, Nanomaterials and interfaces 122(28), 15878 - 15885 (2018) [10.1021/acs.jpcc.8b04262] Files BibTeX | EndNote: XML, Text | RIS
Electrifying model catalysts for understanding electrocatalytic reactions in liquid electrolytes
Nature materials 17(7), 592 - 598 (2018) [10.1038/s41563-018-0088-3] Files BibTeX | EndNote: XML, Text | RIS
In Situ Stability Studies of Platinum Nanoparticles Supported on Ruthenium−Titanium Mixed Oxide (RTO) for Fuel Cell Cathodes
ACS catalysis 8(10), 9675 - 9683 (2018) [10.1021/acscatal.8b02498] Files BibTeX | EndNote: XML, Text | RIS