four-electron/four-proton transfer, which causes sluggish kinetics. Pt-based materials are the state-of-the-art electrocatalysts for ORR due to their outstanding catalytic activity, selectivity, and long-term stability under operating conditions. [1] However, their scarcity and, thus, high cost limit their applications.Accordingly, research on non-noble metal catalysts increased substantially over the past decades. The most promising material classes so far are transitionmetal-nitrogen-carbon complexes [2][3][4] with Fe or Co as the metal center, [5,6] metal-N 4 organometallic complexes [7] or metal-free catalysts such as nitrogen-doped carbon species utilizing carbon nanotubes or graphene. [8][9][10] These catalysts show promising activity; however, they still fall short in their overall performance compared to Pt. Hence, new materials capable of replacing Pt-based catalysts for ORR are yet to be found.One approach in exploring novel materials is to increase their chemical complexity. Multinary metal alloys require a more challenging synthesis pathway, but enable a virtually unlimited amount of different compositions. For instance, over 2 × 10 6 combinations for quinary alloys selected from a list of 50 elements are possible, each with a different composition. Therefore, selection of candidate materials to be tested is necessary, e.g., based on abundance and toxicity of elements. Some of these largely unexplored multinary compositions might show unique physical and chemical properties. For many alloys, comprising typically five principal elements or more, an unexpected stability as a single solid solution phase was observed in spite of their chemical complexity. This stability is usually explained by the so-called high-entropy effect. [11][12][13] The proposed underlying rational include i) stabilization of the multinary single phase due to increasing entropy with an increasing number of constituents, ii) a lattice distortion effect, and iii) sluggish diffusion. [14] This special state of a complex solid solution may result in unusual properties which are not observed for heterogeneous multiphase alloys comprising intermetallic phases. Their advantages in mechanical, physical, and chemical properties such as structural stability [15] as well as corrosion [16] and oxidation resistance have been evaluated over the past years. [17] Potential applications in (electro)catalysis have only been reported for

Complex solid solutions ("high entropy alloys"), comprising five or more principal elements, promise a paradigm change in electrocatalysis due to the availability of millions of different active sites with unique arrangements of multiple elements directly neighbouring a binding site. Thus, strong electronic and geometric effects are induced, which are known as effective tools to tune activity. With the example of the oxygen reduction reaction, we show that by utilising a datadriven discovery cycle, the multidimensionality challenge raised by this catalyst class can be mastered. Iteratively refined computational models predict activity trends around which continuous composition-spread thin-film libraries are synthesised. High-throughput characterisation datasets are then used as input for refinement of the model. The refined model correctly predicts activity maxima of the exemplary model system Ag-Ir-Pd-Pt-Ru. The method can identify optimal complex-solid-solution materials for electrocatalytic reactions in an unprecedented manner.

Complex solid solution (CSS) nanoparticles were recently discovered as efficient electrocatalysts for a variety of reactions. As one of many advantages, they exhibit the potential to replace noble-metal catalysts with multinary combinations of transition metals because they offer formation of new unique and tailorable active sites of multiple elements located next to each other. This Perspective reports on the current state and on challenges of the (combinatorial) synthesis of multinary nanoparticles and advanced electron microscopy characterization techniques for revealing structure–activity correlations on an atomic scale. We discuss what distinguishes this material class from common catalysts to highlight their potential to act as electrocatalysts and rationalize their nontypical electrochemical behavior. We provide an overview about challenges in synthesis, characterization, and electrochemical evaluation and propose guidelines for future design of CSS catalysts to achieve further progress in this research field, which is still in its infancy.

The formation of a vast number of different multielement active sites in compositionally complex solid solution materials, often more generally termed high‐entropy alloys, offers new and unique concepts in catalyst design, which mitigate existing limitations and change the view on structure–activity relations. We discuss these concepts by summarising the currently existing fundamental knowledge and critically assess the chances and limitations of this material class, also highlighting design strategies. A roadmap is proposed, illustrating which of the characteristic concepts could be exploited using which strategy, and which breakthroughs might be possible to guide future research in this highly promising material class for (electro)catalysis.

Background Since the COVID-19 pandemic has affected the education of medical students, medical faculties have faced the challenge of adapting instruction to digital platforms. Although medical students are willing to support pandemic response efforts, how the crisis will affect their medical training remains uncertain. Thus, in this study, we investigated the teaching- and learning-related stressors and expectations of medical students in Germany during the COVID-19 pandemic. Methods A cross-sectional survey was distributed online to undergraduate medical students at medical faculties in Germany. Students answered questions about COVID-19 and teaching (on a 7-point Likert scale from 0 (“not at all”) to 6 (“completely”)) and completed mental well-being measurements, including the State–Trait Anxiety Inventory (STAI), the Generalised Anxiety Disorder scale (GAD-7) and the Perceived Health Questionnaire (PHQ-9). Descriptive data analysis, a t-test and Pearson correlations were performed to process the data. Results Medical students felt well-informed about COVID-19 in general (M = 5.64, SD = 1.28) and in the medical context (M = 5.14, SD = 1.34) but significantly less informed about the pandemic in the academic context, M = 2.47, SD = 1.49, t(371) = 31.98, p < .001. Their distress levels were high (STAI: M = 45.12, SD = 4.73) and significantly correlated with the academic context (rp = .164, p < .01) but not their private lives. Concerning how they were taught, they most often expected online lectures (91.7%) and live broadcasts (67.2%) and less often expected innovative digital teaching strategies, including serious games (17.3%) and virtual-reality exercises (16.7%). Discussion Medical students seem to be aware of the COVID-19 pandemic and its consequences for academic and healthcare contexts. They also seem to think that their teachers will enhance their digital competencies during the pandemic. Therefore, faculties of medicine need to rapidly and adequately digitalise their approaches to teaching.