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.
Green hydrogen - produced from water electrolysis by using sustainable electricity - is getting more attention due to its potential to be used as energy carrier as well as building block for various industrial processes. Among both half-reactions of water electrolysis, Oxygen Evolution Reaction (OER) is kinetically more challenging and it requires advances in the development of innovative electrocatalysts.
A team of scientists from the MPI CPfS in the research field Chemical Metals Sciences prepared a new intermetallic compound by the high-pressure high-temperature technique. From quantum-chemical analysis, this material is formed by chain polyanions of Ge atoms and four-atomic cluster polycations Lu4. It constitutes an important step in the understanding of chemical bonding in intermetallic compounds.
A team lead by scientists from the MPI CPfS developed a novel experimental method that provides direct images of excited states in a transition metal compound without the need for complex calculations. This constitutes a major step for the understanding of the electronic structure and the rich physics of these materials.
Topological materials are characterised by unique electronic and physical properties that are determined by the underlying topology of their electronic systems. Scientists from the Max Planck Institutes for Microstructure Physics (Halle) and for Chemical Physics of Solids (Dresden) have now discovered that (TaSe4)2I is the first material in which a charge density wave induces a phase transition between the semimetal to insulator state.
For the period of 2020 to 2024, Dr. Gudrun Auffermann has been elected Equal Opportunity Commissioner and Renate Hempel-Weber (Physics of Quantum Materials) has been elected Deputy. We congratulate and wish all the best for the exercise of this important office.
Traditionally, the quantum Hall effect has exclusive been associated with two-dimensional metals. Now, scientists at the MPI CPfS found signatures of an unconventional Hall response in the quantum limit of the bulk metal HfTe5, adjacent to the three-dimensional quantum Hall effect of a single electron band at low magnetic ﬁelds.
The intricate interplay of band-formation and electron correlation effects in uranium heavy fermion compounds is subject of an ongoing debate. Here scientists from MPI CPfS in Dresden, University of Cologne, University of Erlangen, Heidelberg University, University of California at San Diego, Los Alamos National Laboratory, Institute of Low…
Johannes Gooth, Leiter der unabhängigen Max-Planck-Forschungsgruppe „Nanostrukturierte Quantenmaterie“ am MPI für Chemische Physik fester Stoffe in Dresden, erhält den Rudolf-Kaiser-Preis für den „erstmaligen experimentellen Nachweis sowie die weitergehende Charakterisierung der axialen Gravitations-Anomalie in Weyl-Halbmetallen“.