Soliman Samuel S, Dey Gaurav R, McCormick Connor R, Schaak Raymond E
ACS Nano. 2023 Aug 22;17(16):16147-16159. doi: 10.1021/acsnano.3c05241. Epub 2023 Aug 7.
Morphology-controlled nanoparticles of high entropy intermetallic compounds are quickly becoming high-value targets for catalysis. Their ordered structures with multiple distinct crystallographic sites, coupled with the "cocktail effect" that emerges from randomly mixing a large number of elements, yield catalytic active sites capable of achieving advanced catalytic functions. Despite this growing interest, little is known about the pathways by which high entropy intermetallic nanoparticles form and grow in solution. As a result, controlling their morphology remains challenging. Here, we use the high entropy intermetallic compound (Pd,Rh,Ir,Pt)Sn, which adopts a NiAs-related crystal structure, as a model system for understanding how nanoparticle morphology, composition, and structure evolve during synthesis in solution using a slow-injection reaction. By performing a time-point study, we establish the initial formation of palladium-rich cube-like Pd-Sn seeds onto which the other metals deposit over time, concomitant with continued incorporation of tin. For (Pd,Rh,Ir,Pt)Sn, growth occurs on the corners, resulting in a sample having a mixture of flower-like and cube-like morphologies. We then synthesize and characterize a library of 14 distinct intermetallic nanoparticle systems that comprise all possible binary, ternary, and quaternary constituents of (Pd,Rh,Ir,Pt)Sn. From these studies, we correlated compositions, morphologies, and growth pathways with the constituent elements and their competitive reactivities, ultimately mapping out a framework that rationalizes the key features of the high entropy (Pd,Rh,Ir,Pt)Sn intermetallic nanoparticles based on those of their simpler constituents. We then validated these design guidelines by applying them to the synthesis of a morphologically pure variant of flowerlike (Pd,Rh,Ir,Pt)Sn particles as well as a series of (Pd,Rh,Ir,Pt)Sn particles with tunable morphologies based on control of composition.
具有形态可控的高熵金属间化合物纳米颗粒正迅速成为催化领域的高价值目标。它们具有多个不同晶体学位点的有序结构，再加上大量元素随机混合产生的“鸡尾酒效应”，产生了能够实现先进催化功能的催化活性位点。尽管对此兴趣日益浓厚，但对于高熵金属间纳米颗粒在溶液中形成和生长的途径却知之甚少。因此，控制它们的形态仍然具有挑战性。在这里，我们使用具有与NiAs相关晶体结构的高熵金属间化合物(Pd,Rh,Ir,Pt)Sn作为模型系统，以了解在溶液中通过慢注射反应合成纳米颗粒时，其形态、组成和结构是如何演变的。通过进行时间点研究，我们确定了富含钯的立方状Pd-Sn晶种的初始形成，随着时间的推移，其他金属会沉积在这些晶种上，同时锡会持续掺入。对于(Pd,Rh,Ir,Pt)Sn，生长发生在角上，导致样品具有花状和立方状形态的混合物。然后，我们合成并表征了一个包含(Pd,Rh,Ir,Pt)Sn所有可能的二元、三元和四元成分的14种不同金属间纳米颗粒系统的库。通过这些研究，我们将组成、形态和生长途径与组成元素及其竞争反应性相关联，最终绘制出一个框架，根据其较简单成分的关键特征来合理化高熵(Pd,Rh,Ir,Pt)Sn金属间纳米颗粒的关键特征。然后，我们通过将这些设计准则应用于合成形态纯的花状(Pd,Rh,Ir,Pt)Sn颗粒变体以及基于组成控制的一系列具有可调形态的(Pd,Rh,Ir,Pt)Sn颗粒，验证了这些设计准则。
