Microscale Combinatorial Libraries for the Discovery of High-Entropy Materials

Polyelemental material systems, specifically high-entropy alloys, promise unprecedented properties. Due to almost unlimited combinatorial possibilities, their exploration and exploitation is hard. This challenge is addressed by co-sputtering combined with shadow masking to produce a multitude of microscale combinatorial libraries in one deposition process. These thin-film composition spreads on the microscale cover unprecedented compositional ranges of high-entropy alloy systems and enable high-throughput characterization of thousands of compositions for electrocatalytic energy conversion reactions using nanoscale scanning electrochemical cell microscopy. The exemplary exploration of the composition space of two high-entropy alloy systems provides electrocatalytic activity maps for hydrogen evolution and oxygen evolution as well as oxygen reduction reactions. Activity optima in the system Ru-Rh-Pd-Ir-Pt are identified, and active noble-metal lean compositions in the system Co-Ni-Mo-Pd-Pt are discovered. This illustrates that the proposed microlibraries are a holistic discovery platform to master the multidimensionality challenge of polyelemental systems.

Automated summary

Polyelemental material systems, specifically high-entropy alloys, have unprecedented properties, but their exploration and exploitation is challenging due to the vast number of possible combinations. However, a method combining co-sputtering and shadow masking allows for the creation of microscale combinatorial libraries, which cover a wide range of compositions and enable high-throughput characterization. By applying this method, electrocatalytic activity maps for hydrogen evolution, oxygen evolution, and oxygen reduction reactions were obtained for two high-entropy alloy systems, identifying activity optima and lean compositions with low noble-metal content. This demonstrates the potential of these microlibraries as a discovery platform for polyelemental systems.