| Apr 20, 2026 |
New three-step method opens a systematic path to next-generation catalyst discovery.
(Nanowerk News) Composed of five or more elements in nearly equal amounts, high-entropy alloys (HEAs) have emerged as promising catalysts due to their compositionally complex surfaces that can accelerate chemical reactions. Until now, scientists have not been able to precisely engineer these surface structures at the nanoscale, making it difficult to study how particle shape influences catalytic performance.
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Now, a study led by Northwestern University professors Chad A. Mirkin and Christopher M. Wolverton has solved that problem.
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A new three-component synthesis strategy enables simultaneous control over both the composition and the high-index surface facets of HEA nanoparticles for the first time.
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Mirkin’s team applied the synthetic method to megalibraries, a nanomaterial synthesis and discovery platform invented and developed by Mirkin, to scale the HEA synthesis to approximately 36 million nanoparticles across 90,000 unique compositions on a single, centimeter-scale chip, opening a high-throughput path to screening and discovering next-generation HEA catalysts with high-index facets (HIFs). Wolverton’s team validated and guided these experiments by performing computational studies to understand the formation and stability of the HEA nanoparticle HIFs.
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The study was published in Journal of the American Chemical Society (“A Three-Component Strategy for Synthesizing High-Entropy Alloy Nanoparticles with High-Index Facets”).
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“High-entropy alloys have been a black box for catalysis because you could never control the surface,” Mirkin said. “We fixed that, and we did it in a way that works across different metals and different chemistries. Then, we scaled it to millions of particles. Now, you can actually study these materials in the way that they deserve to be studied.”
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| Colored scanning electron microscopy image showing multiple high-index-facet high-entropy alloy nanoparticles in the field of view. (Image: International Institute for Nanotechnology)
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Mirkin is the George B. Rathmann Professor of chemistry at Northwestern’s Weinberg College of Arts and Sciences; professor of chemical and biological engineering, biomedical engineering and materials science and engineering at the McCormick School of Engineering; and director of the International Institute for Nanotechnology (IIN). Wolverton is the Frank C. Engelhart Professor of materials science and engineering at McCormick.
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A three-step solution
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The researchers devised a three-step strategy to dictate the shape of the exposed facets on the surface of HEA nanoparticles. High-index facets are characterized by their stepped and kinked atomic arrangements, which provide a greater density of active sites for chemical reactions than the flatter, smoother surfaces of low-index facets. This makes them more reactive and better suited for catalysis. However, high-index facets are less stable and more difficult to engineer, which is why previous synthesis methods consistently produced low-index facets by default.
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The new strategy solves this puzzle in three stages. First, the target metals are combined with liquid gallium, which serves as a nanoscale solvent and enables the formation of a stable, well-mixed alloy. Second, a volatile metal such as tellurium, antimony, or bismuth is introduced to alloy with the particle. Third, most of the volatile metal is evaporated at high temperature, and only a trace amount of the volatile metal remains on the particle surface, shifting the surface energy to favor high-index facet formation and locking the particle into a tetrahexahedral shape. The mechanism was confirmed by density functional theory calculations and demonstrated across seven different multi-metallic systems.
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“The megalibrary lets you search for materials at a scale nobody else can match,” Wolverton said. “What this study adds is the ability to control not just what the particles are made of but how their surfaces are structured. For catalysis, that is the whole game. We are just now in a position to play it properly.”
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Millions of particles, one chip
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Megalibraries are made using arrays of nanoscale tips via processes called polymer pen lithography and scanning probe block copolymer lithography. These tiny tips are used to print millions of unique and distinct nanoreactors onto chips, and each nanoreactor produces a single, composition-controlled HEA nanoparticle. When coupled with the appropriate screening techniques, this approach allows researchers to test millions of material variants for catalytic performance in a single campaign, rather than testing one material at a time.
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Previously, megalibraries were used to identify a commercially viable replacement for scarce and costly iridium-based catalysts in the oxygen evolution reaction, a critical step to clean hydrogen production. Such a breakthrough discovery can be achieved in one afternoon, rather than years with other methods. With the addition of surface structure control, the megalibraries can now be used to explore an even broader range of catalytic materials to find the most effective ones that will solve key societal energy problems.
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What’s next
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“This scientific advancement is providing the Army with rapid ways to synthesize and assess next-generation materials for resilient energy storage and conversion,” said Matthew Glasscott, program manager, U.S. Army Combat Capabilities Development Command Army Research Office.
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With both composition and surface structure now controllable and scalable to millions of particles, researchers can systematically investigate structure-property relationships in HEA catalysts. As artificial intelligence and machine learning are integrated into the megalibrary platform, the pace of discovery in catalysis and related fields is expected to accelerate even further.
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