Frontier Institute of Science and Technology and State Key Laboratory of Multiphase Flow in Power Engineering , Xi'an Jiaotong University , Xi'an , Shaanxi 710049 , China.
Institute of Advanced Electrochemical Energy and School of Materials Science and Engineering , Xi'an University of Technology , Xi'an , Shaanxi 710048 , China.
Nano Lett. 2019 Mar 13;19(3):1743-1748. doi: 10.1021/acs.nanolett.8b04735. Epub 2019 Feb 13.
Synthesis of Pt nanoshells on substrates can increase the utilization efficiency of Pt atoms and reduce the amount of Pt used in the applications. However, it is still an enormous challenge in tailoring the required crystal facets of Pt nanoshells on a given substrate. In this work, we demonstrate a facile and convenient approach capable for generating Pt octahedral islands with tunable sizes and densities on Pd nanocubes by manipulating the deposition rate. The key to this synthesis is the fine control over the deposition rate of Pt on Pd seeds. Because of the different reactivities at the surface sites, the deposition of Pt can be controlled at a certain site by carefully tuning the deposition rate. With a low concentration of reductant (8.33 mg/mL of glucose), surface diffusion dominates the process, and thus the Pt cubic shells form on Pd cubic seeds. In contrast, when a higher amount of the reductant (16.67 mg/mL of glucose) is added, the deposition starts to dominate the growth of Pt shells. In this case, the deposition would be controlled at the corners, forming eight large Pt octahedra on a cubic Pd seed. Further increasing the deposition rate can induce much higher deposition rates, in which case, the deposition of Pt would likely take place not only at the corners, but also the edge and surface sites of the seeds. Not surprisingly, this growth habit can result in the formation of high-density octahedral islands on Pd cubic seeds. With the same amount of precursor supply, the higher the densities of Pt islands, the smaller the size of the octahedral islands on Pd nanocubes. Unlike other synthetic methods, the size of the octahedral islands on Pd seeds can be even controlled to be smaller than 3 nm by controlling the amount of the Pt precursor. Considering the excellent performance of {111} facets of Pt catalysts toward ORR, the Pt nanocages with small octahedral islands on the surfaces can exhibit a high activity with a mass activity 0.68 A/mg, as high as 5.2 times of that of commercial Pt/C.
在基底上合成 Pt 纳米壳可以提高 Pt 原子的利用率并减少应用中 Pt 的使用量。然而，在给定的基底上定制所需的 Pt 纳米壳晶面仍然是一个巨大的挑战。在这项工作中，我们展示了一种简单方便的方法，通过控制沉积速率，可以在 Pd 纳米立方体上生成具有可调尺寸和密度的 Pt 八面体岛。这种合成的关键是精细控制 Pt 在 Pd 种子上的沉积速率。由于表面位点的反应性不同，可以通过仔细调整沉积速率来控制 Pt 在特定位置的沉积。在低浓度还原剂（8.33 mg/mL 葡萄糖）的情况下，表面扩散占主导地位，因此 Pt 立方壳在 Pd 立方种子上形成。相比之下，当添加更高量的还原剂（16.67 mg/mL 葡萄糖）时，沉积开始主导 Pt 壳的生长。在这种情况下，沉积将在角部控制，在立方 Pd 种子上形成八个大的 Pt 八面体。进一步提高沉积速率会导致更高的沉积速率，在这种情况下，Pt 的沉积可能不仅发生在角部，还会发生在种子的边缘和表面部位。毫不奇怪，这种生长习性会导致在 Pd 立方种子上形成高密度的八面体岛。在相同的前体供应下，Pt 岛的密度越高，Pd 纳米立方体上的八面体岛的尺寸就越小。与其他合成方法不同，通过控制 Pt 前体的量，可以将 Pd 种子上的八面体岛的尺寸甚至控制到小于 3nm。考虑到 Pt 催化剂的 {111} 面在 ORR 中的优异性能，表面具有小八面体岛的 Pt 纳米笼可以表现出高活性，质量活性为 0.68 A/mg，是商业 Pt/C 的 5.2 倍。
