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Abstract: Medium- and high-entropy alloys (MEAs and HEAs) are the basis of unique electrocatalysts for hydrogen-evolution reactions (HERs) due to their tunable chemical compositions and microstructures. Here, various Cantor MEAs (CoFeNi, CoFeNiMn, CoFeNiCr) and a HEA (CoFeNiMnCr) made up of affordable non-noble transitional metals with different structures (primary matrix and secondary phases, grain sizes, lattice parameters) were successfully synthesized with an inert-gas melting process. A close correlation was established between their physicochemical properties (elemental composition, microstructure, crystal structure) and the hydrogen-binding ability of the elements in the alloy on the electrocatalytic HER activity and stability in alkaline and acidic media. Advanced performances of electrocatalysts toward HERs were revealed in a specially designed electrochemical cell. Effectively identifying these electrocatalytic trends lays the groundwork for the strategic design of multi-component alloy electrocatalysts for practical HERs.
Keywords: water-spliting, hydrogen-binding energy, medium-entropy alloys, high-entropy alloys, spillover effect
Published in DiRROS: 10.11.2025; Views: 350; Downloads: 175
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Abstract: Electrochemical water-splitting is a promising green technology for the production of hydrogen. One of the bottlenecks, however, is the oxygen evolution half-reaction (OER), which could be overcome with the development of a suitable electrocatalyst. Recently, non-noble metal, high-entropy oxides (HEO) have been investigated as potential OER electrocatalysts, but complex synthesis approaches that usually produce the material in powder form limit their wider utilization. Here, an innovative synthesis strategy of formulating a nanostructured (CoFeNiMnCr)3O4 HEO thin film on a CoFeNiMnCr high entropy alloy (HEA) using facile electrochemical and thermal treatment methods is presented. The CoFeNiMnCr HEA serves as exceptional support to be electrochemically treated in an ethylene glycol electrolyte with ammonium fluoride to form a rough and microporous structure with nanopits. The electrochemically treated CoFeNiMnCr HEA surface is more prone to oxidation during a low-temperature thermal treatment, leading to the growth of a spinel (CoFeNiMnCr)3O4 HEO thin film. The (CoFeNiMnCr)3O4 HEO exhibits a superior overpotential of 341 mV at 10 mA cm−2 and a Tafel slope of 50 mV dec−1 along with remarkable long-term stability in alkaline media. The excellent catalytic activity and stability for the OER can serve as a promising platform for the practical utilization of (CoFeNiMnCr)3O4 HEO.
Keywords: electrochemical water-spliting, electrocatalysts
Published in DiRROS: 20.12.2024; Views: 1329; Downloads: 468
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