Pittkowski Rebecca K, Clausen Christian M, Chen Qinyi, Stoian Dragos, van Beek Wouter, Bucher Jan, Welten Rahel L, Schlegel Nicolas, Mathiesen Jette K, Nielsen Tobias M, Du Jia, Rosenkranz Asger W, Bøjesen Espen D, Rossmeisl Jan, Jensen Kirsten M Ø, Arenz Matthias
Center for High Entropy Alloy Catalysis (CHEAC), Department of Chemistry, University of Copenhagen Copenhagen Denmark
Swiss Norwegian Beamline, European Synchrotron Radiation Facility (ESRF) Grenoble France.
EES Catal. 2023 Aug 22;1(6):950-960. doi: 10.1039/d3ey00201b. eCollection 2023 Nov 2.
High entropy alloys (HEAs) are an important new material class with significant application potential in catalysis and electrocatalysis. The entropy-driven formation of HEA materials requires high temperatures and controlled cooling rates. However, catalysts in general also require highly dispersed materials, , nanoparticles. Only then a favorable utilization of the expensive raw materials can be achieved. Several recently reported HEA nanoparticle synthesis strategies, therefore, avoid the high-temperature regime to prevent particle growth. In our work, we investigate a system of five noble metal single-source precursors with superior catalytic activity for the oxygen reduction reaction. Combining X-ray powder diffraction with multi-edge X-ray absorption spectroscopy, we address the fundamental question of how single-phase HEA nanoparticles can form at low temperatures. It is demonstrated that the formation of HEA nanoparticles is governed by stochastic principles and the inhibition of precursor mobility during the formation process favors the formation of a single phase. The proposed formation principle is supported by simulations of the nanoparticle formation in a randomized process, rationalizing the experimentally found differences between two-element and multi-element metal precursor mixtures.
高熵合金（HEAs）是一类重要的新型材料，在催化和电催化领域具有巨大的应用潜力。熵驱动的高熵合金材料形成需要高温和可控的冷却速率。然而，一般来说催化剂也需要高度分散的材料，即纳米颗粒。只有这样才能实现对昂贵原材料的良好利用。因此，最近报道的几种高熵合金纳米颗粒合成策略避免了高温条件以防止颗粒生长。在我们的工作中，我们研究了一种由五种具有优异氧还原反应催化活性的贵金属单源前驱体组成的体系。结合X射线粉末衍射和多边缘X射线吸收光谱，我们解决了单相高熵合金纳米颗粒如何在低温下形成这一基本问题。结果表明，高熵合金纳米颗粒的形成受随机原理支配，并且在形成过程中抑制前驱体迁移有利于单相的形成。所提出的形成原理得到了随机过程中纳米颗粒形成模拟的支持，解释了实验发现的二元和多元金属前驱体混合物之间的差异。
