High-entropy alloy nanoparticles (HEA NPs) emerged as catalysts with superior performances that are not shown in monometallic catalysts. Although many kinds of synthesis techniques of HEA NPs have been developed recently, synthesizing HEA NPs with ultrasmall particle size and narrow size distribution remains challenging because most of the reported synthesis methods require high temperatures that accelerate particle growth. This work provides a new methodology for the fabrication of ultrasmall and homogeneous HEA NPs using a continuous-flow reactor with a liquid-phase reduction method. We successfully synthesized ultrasmall IrPdPtRhRu HEA NPs (1.32 ± 0.41 nm), theoretically each consisting of approximately 50 atoms. This average size is the smallest ever reported for HEA NPs. All five elements are homogeneously mixed at the atomic level in each particle. The obtained HEA NPs marked a significantly high hydrogen evolution reaction (HER) activity with a very small 6 mV overpotential at 10 mA/cm^–2 in acid, which is one-third of the overpotential of commercial Pt/C. In addition, although mass production of HEA NPs is still difficult, this flow synthesis can provide high productivity with high reproducibility, which is more energy efficient and suitable for mass production. Therefore, this study reports the 1 nm-sized HEA NPs with remarkably high HER activity and establishes a platform for the production of ultrasmall and homogeneous HEA NPs.

中文翻译：

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用于均质 1 nm 尺寸极小高熵合金纳米粒子的连续流动反应器合成

高熵合金纳米粒子（HEA NPs）作为催化剂出现，具有单金属催化剂所没有的优异性能。尽管最近已经开发了多种 HEA NPs 的合成技术，但合成具有超小粒径和窄尺寸分布的 HEA NPs 仍然具有挑战性，因为大多数报道的合成方法都需要高温来加速粒子生长。这项工作为使用具有液相还原方法的连续流动反应器制造超小型和均匀的 HEA NPs 提供了一种新方法。我们成功合成了超小 IrPdPtRhRu HEA NPs (1.32 ± 0.41 nm)，理论上每个由大约 50 个原子组成。这个平均大小是 HEA NPs 报告的最小的。所有五种元素在每个粒子的原子水平上均匀混合。获得的 HEA NPs 具有显着高的析氢反应 (HER) 活性，在 10 mA/cm 时具有非常小的 6 mV 过电位^–2在酸中，是商业 Pt/C 过电位的三分之一。此外，虽然 HEA NPs 的大规模生产仍然很困难，但这种流动合成可以提供高生产率和高重现性，更节能，适合大规模生产。因此，本研究报告了具有非常高的 HER 活性的 1 nm 尺寸的 HEA NPs，并为生产超小和均质的 HEA NPs 建立了平台。