Phase-Controlled Deposition of Ru on Pd Nanocrystal Templates: Effects of Particle Shape and Size
Phase-Controlled Deposition of Ru on Pd Nanocrystal Templates: Effects of Particle Shape and Size
复制标题
DOI：
10.1021/acs.jpcc.2c08825
复制
发表时间：
2023-01
期刊：
影响因子：
--
通讯作者：
A. Janssen;Quynh N. Nguyen;Zhiheng Lyu;Veronica D. Pawlik;Chenxiao Wang;Younan Xia
中科院分区：
文献类型：
--
作者：
A. Janssen;Quynh N. Nguyen;Zhiheng Lyu;Veronica D. Pawlik;Chenxiao Wang;Younan Xia
模板定向生长已被广泛应用于金属纳米晶体的相控制合成，但其机理细节仍有待进一步研究。在这项工作中，我们系统地研究了Pd纳米晶模板的形状和大小在控制沉积的Ru覆盖层所采取的晶相方面所起的作用。对于Pd立方纳米晶，当颗粒尺寸在6-25 nm范围内变化时，总是倾向于面心立方(FCC)Ru壳层。对于Pd八面体纳米晶体，我们观察到了尺寸依赖关系，14 nm的八面体产生FCC-Ru，而20和26 nm的八面体产生六方紧密堆积(HCP)Ru。这一趋势可以归因于它们在表面原子排列上的不同，因为立方模板上的{100}面不能被hcp-Ru的任何面匹配，迫使沉积的Ru采取面心立方相。相反，八面体模板上的{111}面可以与hcp-Ru的{0001}面匹配，从而允许沉积的Ru具有hcp或fcc相。Ru壳层所取的晶相由沉积的面心立方和六方Ru相的表面能和体能的相对贡献决定。此外，反应混合物中的水含量也通过改变还原动力学来影响Ru壳层的晶相。当作为乙二醇氧化催化剂时，fcc-Ru的性能优于hcp-Ru，而立方体形状优于八面体。
Template-directed growth has been widely used for the phase-controlled synthesis of metal nanocrystals, but much remains to be discovered about the mechanistic details. In this work, we systematically investigate the roles played by the shape and size of Pd nanocrystal templates in controlling the crystal phase taken by the deposited Ru overlayers. For Pd cubic nanocrystals, a face-centered cubic (fcc) Ru shell is always favored when the particle size is varied in the range of 6–25 nm. In the case of Pd octahedral nanocrystals, we observe a size dependence, with 14-nm octahedra giving fcc-Ru but 20- and 26-nm octahedra resulting in hexagonal close-packed (hcp) Ru. This trend can be attributed to their difference in surface atomic arrangement, as the {100} facets on a cubic template cannot be matched by any facet of hcp-Ru, forcing the deposited Ru to take the fcc phase. In contrast, the {111} facets on an octahedral template can be matched by the {0001} facets of hcp-Ru, allowing the deposited Ru to take either an hcp or fcc phase. The crystal phase taken by the Ru shell is determined by the relative contributions from the surface and bulk energies of the deposited fcc- and hcp-Ru phases. Additionally, the water content in the reaction mixture also plays an important role in affecting the crystal phase taken by the Ru shell by altering the reduction kinetics. When tested as catalysts toward ethylene glycol oxidation, the fcc-Ru outperforms hcp-Ru, while the cubic shape is advantageous over the octahedral counterpart.