Discovery of High-Entropy Oxide Electrocatalysts: From Thin-Film Material Libraries to Particles

[Image: see text] Discovery of new high-entropy electrocatalysts requires testing of hundreds to thousands of possible compositions, which can be addressed most efficiently by high-throughput experimentation on thin-film material libraries. Since the conditions for high-throughput measurements (“screening”) differ from more standardized methods, it is frequently a concern whether the findings from screening can be transferred to the commonly used particulate catalysts. We demonstrate the successful transfer of results from thin-film material libraries to particles of Cantor alloy oxide (Co-Cr-Fe-Mn-Ni)(3)O(4). The chemical compositions of the libraries, all single-phase spinels, cover a wide compositional range of (Cr(8.1–28.0)Mn(11.6–28.4)Fe(10.6–39.0)Co(11.4–36.7)Ni(13.5–31.4))(37.7±0.6)O(62.3±0.6), with composition-dependent lattice constant values ranging from 0.826 to 0.851 nm. Electrochemical screening of the libraries for the oxygen evolution reaction (OER) identifies (Cr(24.6±1.4)Mn(15.7±2.0)Fe(16.9±1.8)Co(26.1±1.9)Ni(16.6±1.7))(37.8±0.8)O(62.2±1.2) as the most active composition, exhibiting an overpotential of 0.36 V at a current density of 1 mA cm(–2). This “hit” in the library was subsequently synthesized in the form of particles with the same composition and crystal structure using an aerosol-based synthesis strategy. The similar OER activity of the most active thin-film composition and the derived catalyst particles validates the proposed approach of accelerated discovery of novel catalysts by screening of thin-film libraries.