Complex‐Solid‐Solution Electrocatalyst Discovery by Computational Prediction and High‐Throughput Experimentation**

Abstract

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.

Bayesian Optimization of High‐Entropy Alloy Compositions for Electrocatalytic Oxygen Reduction**

“…All linear sweep voltammograms (LSVs) are available in Figure S9. We note that catalytic trends on the quinary alloys obtained with the same experimental setup have been reported previously [4] . Therefore the scope of the current study is on the verification of the discovered optimal compositions.…”

“…High‐entropy alloys (HEAs; in the form of single‐phase compositionally complex solid solutions) offer a vast composition space for optimization of catalytic properties [1–5] . The many multi‐element atomic surface sites found on such complex surfaces contribute to a near‐continuum of the reaction intermediate adsorption energies that are descriptive of catalytic activity.…”

Bayesian Optimization of High‐Entropy Alloy Compositions for Electrocatalytic Oxygen Reduction**

“…High‐entropy alloys (HEAs; in the form of single‐phase compositionally complex solid solutions) offer a vast composition space for optimization of catalytic properties. [ 1 , 2 , 3 , 4 , 5 ] The many multi‐element atomic surface sites found on such complex surfaces contribute to a near‐continuum of the reaction intermediate adsorption energies that are descriptive of catalytic activity. Tailoring the HEA composition can improve the distribution of these adsorption energies to yield better catalysts.…”

Searching novel complex solid solution electrocatalysts in unconventional element combinations

“…Various research groups are recently reporting the characterization of specific multielement alloys having unique properties, for example a high catalytic activity or stability [4,5], showing exceptional mechanical strength and ductility [6], or describing novel synthesis methods of multinary alloys [7][8][9][10]. As ISSN 1998-0124 CN 11-5974/O4 https://doi.org/10.1007/s12274-021-3637-z possible catalyst materials, high entropy materials were already successfully applied to the hydrogen evolution reaction (HER) [5,9,11], the oxygen evolution reaction (OER) [11,12], carbon monoxide reduction [13], carbon dioxide reduction [13,14] and the oxygen reduction reaction (ORR) [15][16][17], methanol oxidation [18,19], ammonia synthesis and decomposition [20,21].…”