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

Abstract

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 singlephase 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 f o r t h e o x y g e n e v o l u t i o n r e a c t i o n ( O E R ) i d e n t i fi e s ( C r 2 4 . 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.

Acidic Hydrogen Evolution Electrocatalysis at High‐Entropy Alloys Correlates with its Composition‐Dependent Potential of Zero Charge

“…The Pt−Pd−Ru−Ir−Ag ML was prepared by a single combinatorial co‐sputtering process of all elements on a silicon wafer [5] . Simultaneous sputtering of multiple elements has successfully been used to fabricate thin‐film type HEA libraries consisting of noble metals, [5,24] non‐noble metals, [40] and oxides [41] with a continuous compositional gradient of each element. Their atomic level mixing has been characterized by energy dispersive X‐ray analysis (EDX) and atom probe tomography (APT) [5,24] .…”

Questing for High‐Performance Electrocatalysts for Oxygen Evolution Reaction: Importance of Chemical Complexity, Active Phase, and Surface‐Adsorbed Species

“…In addition to anion doping, multi‐cation doping is also a way to generate strain. For instance, the lattice constant of a high‐entropy spinel oxide (Co−Cr−Fe−Mn−Ni) 3 O 4 changes significantly with the cation composition, suggesting presence of different lattice strains induced by alloying various cations of different ionic sizes and proportions [16] . However, the effect of strain on the OER activity was not explored in [16], which deserves further investigation.…”

Die Elektrokatalyse der Wasserstoffentwicklung im Sauren an Hochentropielegierungen korreliert mit dem von der Zusammensetzung abhängigen Nullladungspotential

“…Die PtÀ PdÀ RuÀ IrÀ AgÀ ML wurde durch einen kombinatorischen Co-Sputterprozess aller Elemente auf einem Siliziumwafer hergestellt. [5] Das gleichzeitige Sputtern mehrerer Elemente wurde erfolgreich zur Herstellung von Dünnschicht-HEA-Bibliotheken verwendet, die aus Edelmetallen, [5,24] Nicht-Edelmetallen [40] und Oxiden [41] mit einem kontinuierlichen Zusammensetzungsgradienten jedes Elements bestehen. Die Durchmischung auf atomarer Skala wurde durch energiedispersive Röntgenanalyse (EDX) und Atomsondentomographie (APT) charakterisiert.…”