The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University , Atlanta, Georgia 30332, United States.
State Key Laboratory of Silicon Materials and Department of Materials Science and Engineering, Zhejiang University , Hangzhou, Zhejiang 310027, People's Republic of China.
ACS Appl Mater Interfaces. 2017 Sep 13;9(36):31203-31212. doi: 10.1021/acsami.7b12018. Epub 2017 Aug 31.
This article reports the design and successful implementation of a one-pot, polyol method for the synthesis of penta-twinned Pd nanowires with diameters below 8 nm and aspect ratios up to 100. The key to the success of this protocol is the controlled reduction of NaPdCl by diethylene glycol and ascorbic acid through the introduction of NaI and HCl. The I and H ions can slow the reduction kinetics by forming PdI and inhibiting the dissociation of ascorbic acid, respectively. When the initial reduction rate is tuned into the proper regime, Pd decahedral seeds with a penta-twinned structure appear during nucleation. In the presence of I ions as a selective capping agent toward the Pd(100) surface, the decahedral seeds can be directed to grow axially into penta-twinned nanorods and then nanowires. The Pd nanowires are found to evolve into multiply twinned particles if the reaction time is extended beyond 1.5 h, owing to the involvement of oxidative etching. When supported on carbon, the Pd nanowires show greatly enhanced specific electrocatalytic activities, more than five times the value for commercial Pd/C toward formic acid oxidation and three times the value for Pt/C toward oxygen reduction under an alkaline condition. In addition, the carbon-supported Pd nanowires exhibit greatly enhanced electrocatalytic durability toward both reactions. Furthermore, we demonstrate that the Pd nanowires can serve as sacrificial templates for the conformal deposition of Pt atoms to generate Pd@Pt core-sheath nanowires and then Pd-Pt nanotubes with a well-defined surface structure.
本文报道了一种一锅多醇法合成直径小于 8nm、纵横比高达 100 的五孪晶 Pd 纳米线的设计与成功实施。该方法的关键在于通过引入 NaI 和 HCl，控制 NaPdCl4 被二甘醇和抗坏血酸还原。I 和 H 离子可以通过形成 PdI 和抑制抗坏血酸的离解，分别减缓还原动力学。当初始还原速率被调至适当范围时，在成核过程中会出现具有五孪晶结构的 Pd 十面体种子。在 I 离子作为 Pd(100)表面选择性封端剂的存在下，这些十面体种子可以定向轴向生长为五孪晶纳米棒，然后是纳米线。如果反应时间延长至 1.5 小时以上，由于氧化刻蚀的参与，Pd 纳米线会演变成多孪晶颗粒。当负载在碳上时，Pd 纳米线表现出大大增强的特定电催化活性，对于甲酸氧化，其活性比商业 Pd/C 高 5 倍，对于碱性条件下的氧还原，其活性比 Pt/C 高 3 倍。此外，负载在碳上的 Pd 纳米线在这两种反应中都表现出大大增强的电催化耐久性。此外，我们证明了 Pd 纳米线可以作为 Pt 原子的牺牲模板，用于生成具有良好表面结构的 Pd@Pt 核壳纳米线和 Pd-Pt 纳米管。
