The water electrolysis is an electrochemical way for production of hydrogen, which is considered as one of the future energy carrier molecules. Therefore, looking at numerous advantages of proton exchange membrane electrolysis compared to the classical alkaline variant, it’s efficiency and applicability on the large scale is of huge importance nowadays. However, the slow kinetics of the anode oxygen evolution reaction (OER) limits the overall electrolysis process and requires an active and stable electrocatalyst. Such need inspired the scientists of Chemical Metal Science and Physics of Correlated Matter departments at MPI CPfS together with the Fritz-Haber-Institut in Berlin to employ their longstanding expertise in chemistry of intermetallic compounds, electronic features of solid matter and electrocatalysis to make a step forward in this challenging direction. As a result of fruitful teamwork, the concept of cooperative phases with different stabilities under OER conditions was successfully demonstrated with the intermetallic compound Hf2B2Ir5 as a self-optimizing electrocatalyst for OER.
Based on chemical bonding analysis, the intermetallic compound Hf2B2Ir5 has a cage-like type of the crystal structure: the two-dimensional layers of B2Ir8 units are interconnected by two- and three-center Ir-Ir interactions to polyanionic framework and hafnium atoms are guesting in such anionic cages. The atomic interactions features are reflected in the electronic structure of Hf2B2Ir5 and its chemical behaviour under OER conditions. The initial electrochemical OER activity of Hf2B2Ir5 sustains during the continuous operation at elaborated current densities of 100 mA cm-2 for at least 240 h (Figure 1) and positions this material among Ir-based state-of-the-art electrocatalysts. The harsh oxidative conditions of OER activate the surface-limited changes of the pristine material and as a result the electrochemical performance is related to the cooperative work of Ir-terminated surface of the ternary compound itself and agglomerates of IrOx(OH)y(SO4)z particles (inset of Figure 1). The latter are formed mainly due to the oxidation of HfB4Ir3 secondary phase and near-surface oxidation of the investigated compound. The presence of at least two OER-active states of Ir, originated from the Hf2B2Ir5 under OER conditions, was confirmed by the XPS analysis (Figure 2). The experimental data (electrochemical results, material characterization using bulk-and surface-sensitive methods, elemental analysis of the used electrolyte) are consistent with the chemical bonding analysis. The illustrated concept of cooperative phases with different chemical stabilities under OER conditions can be explored to other systems and offers a perspective knowledge-based way for discovery of new effective OER-electrocatalysts.
Iryna Antonyshyn/IA
Figure 1. OER performance of Hf2B2Ir5 anode material, represented by linear sweep voltammograms measured during the long-term chronopotentiometry experiment (0.1 M H2SO4, j = 100 mA cm-2, t = 0 ... 240 h). Inset: morphology of Hf2B2Ir5 material afterwards.
Figure 1. OER performance of Hf2B2Ir5 anode material, represented by linear sweep voltammograms measured during the long-term chronopotentiometry experiment (0.1 M H2SO4, j = 100 mA cm-2, t = 0 ... 240 h). Inset: morphology of Hf2B2Ir5 material afterwards.
Figure 2. Ir 4f core levels in Hf2B2Ir5 material: pristine state (black) and after 240 h of chronopotentiometry at 100 mA cm-2 current density (pink). The reference lines are drawn for Ir 4f in intermetallic Hf2B2Ir5 (black dashed), elemental Ir (grey dashed) and rutile IrO2 (red dashed).
Figure 2. Ir 4f core levels in Hf2B2Ir5 material: pristine state (black) and after 240 h of chronopotentiometry at 100 mA cm-2 current density (pink). The reference lines are drawn for Ir 4f in intermetallic Hf2B2Ir5 (black dashed), elemental Ir (grey dashed) and rutile IrO2 (red dashed).
Dr. Qingge Mu from the Solid State Chemistry Department has left our institute in December 2021. She has taken up an associate professor position at the Institute of Physical Science and Information Technology at the Anhui University, Hefei, China. We wish Qingge all the best for her future career.
In an international collaboration, scientists of MPI CPfS have used state-of-the-art 3D printing and microscopy to provide a new glimpse of what happens when taking magnets to three-dimensions on the nanoscale – 1000 times smaller than a human hair. The studied magnetic double helices produce topological textures in the magnetic field, opening the door to the next generation of magnetic devices.
The Max Born Prize, jointly awarded by the British Institute of Physics (IOP) and the DPG for particularly valuable and timely scientific contributions to physics, will be awarded in 2022 to Prof. Dr. Claudia Felser of the Max Planck Institute for Chemical Physics of Solids, Dresden.
Discovery and analysis of superconductivity in new classes of materials not only broadens fundamental knowledge of this phenomenon, but also brings us closer to unlocking their full application potential. In particular, unconventional superconductors offer new perspective on this century-old concept.
Researchers at the Max Planck Institute for Chemical Physics of Solids in Dresden, Germany, together with collaborators at the Ohio State University and the University of Cincinnati, have discovered, for the first time, a giant thermoelectric effect in an antiferromagnet.
The Max Planck Institute for Chemical Physics of Solids welcomes Dr. Claire Donnelly as group leader of a newly established Lise Meitner Research Group at the MPI CPfS!
Lead telluride is an important thermoelectric material but its metal-to-semiconductor transition above 230 °C is not fully understood. Here, atomic-resolution transmission electron microscopy provides structural insights into this transition, explaining the metallic behavior by local structural changes leading to the formation of a dislocation network within the rock salt structure.
Recent research suggested that hydrodynamic electron flow in 3D conductors was possible, but exactly how it happened or how to observe it remained unknown. Until now. A team of researchers from Harvard, MIT and the Max Planck Institute Chemical Physics of Solids developed a theory to explain how hydrodynamic electron flow could occur in 3D materials and observed it for the first time using a new imaging technique.
The Microscopy Conference 2021 (MC2021) was held in digital format from August 22nd to 26th 2021 organized by TU Wien. The Microscopy Conference MC2021 is the largest and most important scientific event on this area in Europe and offers fascinating information about mainly electron microscopy methods and their applications in life sciences or materials sciences with over 700 participants from about 40 countries.
Über 5.000 Läufer haben am Mittwochabend am ersten Tag der REWE-Team-Challenge teilgenommen. Das MPI CPfS war mit 16 Laufbegeisterten in schicken neuen Shirts in den Max-Planck Farben mit dabei! In vier Teams, einem Frauen- und drei Männerteams, ging es auf der 5 km langen Strecke vom Kulturpalast durch die historische Innenstadt Dresdens zum Rudolf-Harbig-Stadion. Alle haben die stimmungsvolle Laufstrecke genossen und unser Frauenteam hat es fast in die Top 10 geschafft (Platz 14)!
