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.
VO 2 -based thin-film libraries with a continuous composition spread of Cr were obtained by reactive cosputtering. Gradual changes in the crystalline structures of VO 2 were observed in the thin-film libraries at room temperature as the M1 phase exists for Cr < 1.2 at. %, the M2 phase for Cr > 4.2 at. %, and the T phase in between. Although X-ray diffraction indicates that only VO 2 phases exist in the library, X-ray photoelectron spectroscopy reveals an increased V 5+ /V 4+ ratio with increasing Cr content along the V−Cr−O library. A V−Cr−O phase diagram was assessed based on the results of temperature-dependent X-ray diffraction of the libraries. Microstructures of the V−Cr−O libraries were studied by scanning electron microscopy and atomic force microscopy. High-throughput temperature-dependent electrical resistance [R(T)] and stress [σ(T)] measurements were performed on the V−Cr−O libraries to systematically study the influence of Cr on the transformation properties. The transformation temperature T c was increased by 4.9 K/at. % in the composition range 2.8 at. % < Cr < 7.3 at. % and by 1.2 K/at. % for Cr > 7.3 at. %. The resistance change across the phase transformation was decreased from 3 to 1 order of magnitude with Cr content increasing from 1.1 at. % up to 12.6 at. %, and the R(T) curves became less abrupt. The addition of Cr increased the stress change across the phase transformation up to 1.3 GPa for a Cr content of 3.3 at. %. However, for increased Cr contents from 3.3 to 9 at. %, the stress change decreased to 380 MPa. This could be because of the increased fraction of an O-rich VO x phase in the films and a changed crystallographic orientation for Cr-rich V−Cr−O.
The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adem.202201050.
Compositionally complex perovskites provide the opportunity to develop stable and active catalysts for electrochemical applications. The challenge lies in the identification of single‐phase perovskites with optimized composition for high electrical conductivity. Leveraging a recently discovered effect of self‐organized thin film growth during reactive sputtering, La–Co–Mn–O and La–Co–Mn–Fe–O perovskite (ABO3) thin‐film materials libraries are synthesized. These show phase‐pure La perovskites over a wide range of chemical composition variation for the B‐site elements for deposition temperatures ≥300 °C. It is demonstrated that this approach enables the discovery and tailoring of chemical compositions for desired optical bandgap and electrical conductivity and thereby opens the path for the targeted development of, for example, new high‐performance electrocatalysts.
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