A novel mechanism for metal alloying at the nanoscale

Abstract

The controllable incorporation of multiple immiscible elements into a single nanoparticle merits untold scientific and technological potential, yet remains a challenge using conventional synthetic techniques. We propose a novel mechanism for metal alloying at the nanoscale, which provides a general route for alloying dissimilar elements into single-phase solid-solution nanoparticles, referred to as high-entropy-alloy nanoparticles (HEA-NPs). To validate the theory, we developed a facile carbothermal shock (CTS) method to synthesize a wide range of multicomponent (up to eight dissimilar elements) nanoparticles with a desired chemistry (composition), size, and phase (solid solution, phase-separated) by controlling the CTS parameters (substrate, temperature, shock duration, and heating/cooling rate). To prove utility, we synthesized quinary HEA-NPs as ammonia oxidation catalysts with -100% conversion and >99% nitrogen oxide selectivity over prolonged operations. This mechanism is distinct from previously reported alloying processes, which can bring about a new repertoire of alloys and nanostructures with unprecedented functionalities.