Atomic layer-by-layer deposition of Pt on Pd nanocubes for catalysts with enhanced activity and durability toward oxygen reduction.
Atomic layer-by-layer deposition of Pt on Pd nanocubes for catalysts with enhanced activity and durability toward oxygen reduction.
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DOI：
10.1021/nl501205j
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发表时间：
2014-05
期刊：
影响因子：
10.8
通讯作者：
Shuifen Xie;Sang‐Il Choi;N. Lu;Luke T. Roling;J. Herron;Lei Zhang;Jinho Park;Jinguo G Wang
中科院分区：
文献类型：
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作者：
Shuifen Xie;Sang‐Il Choi;N. Lu;Luke T. Roling;J. Herron;Lei Zhang;Jinho Park;Jinguo G Wang
在保持铂基催化剂活性的同时降低铂含量的有效策略是将铂原子作为仅几个原子层厚的超薄皮沉积在由另一种金属制成的纳米级基底上。然而，在沉积过程中，由于 Pt 原子之间的强键合，Pt 原子通常采取岛状生长模式。在这里，我们报告了一种在溶液相中将 Pt 保形沉积为 Pd 纳米立方体上均匀、超薄壳的通用途径。以相对较慢的速率和较高的温度引入 Pt 前驱体，使沉积的 Pt 原子遍布 Pd 纳米立方体的整个表面，从而生成均匀的壳。通过改变添加到系统中的 Pt 前驱体的量，可以将 Pt 壳的厚度控制在 1 到 6 个原子层之间。与商用 Pt/C 催化剂相比，Pd@PtnL (n = 1-6) 核壳纳米立方体表现出比活性和氧还原反应 (ORR) 耐久性的增强。模型 (100) 表面的密度泛函理论 (DFT) 计算表明，比活性的增强可归因于通过配体和应变效应减弱 OH 结合，从而增加 OH 氢化速率。推导了 ORR 比活度与 Pt 原子层数之间的火山型关系，与实验结果非常吻合。理论和实验研究表明，基于 Pd@Pt2-3L 纳米立方体的催化剂的 ORR 比活性最大化。由于 Pt 用量的减少和比活性的增强，Pd@Pt1L 纳米立方体的 Pt 质量活性相对于 Pt/C 催化剂几乎提高了三倍。
An effective strategy for reducing the Pt content while retaining the activity of a Pt-based catalyst is to deposit the Pt atoms as ultrathin skins of only a few atomic layers thick on nanoscale substrates made of another metal. During deposition, however, the Pt atoms often take an island growth mode because of a strong bonding between Pt atoms. Here we report a versatile route to the conformal deposition of Pt as uniform, ultrathin shells on Pd nanocubes in a solution phase. The introduction of the Pt precursor at a relatively slow rate and high temperature allowed the deposited Pt atoms to spread across the entire surface of a Pd nanocube to generate a uniform shell. The thickness of the Pt shell could be controlled from one to six atomic layers by varying the amount of Pt precursor added into the system. Compared to a commercial Pt/C catalyst, the Pd@PtnL (n = 1-6) core-shell nanocubes showed enhancements in specific activity and durability toward the oxygen reduction reaction (ORR). Density functional theory (DFT) calculations on model (100) surfaces suggest that the enhancement in specific activity can be attributed to the weakening of OH binding through ligand and strain effects, which, in turn, increases the rate of OH hydrogenation. A volcano-type relationship between the ORR specific activity and the number of Pt atomic layers was derived, in good agreement with the experimental results. Both theoretical and experimental studies indicate that the ORR specific activity was maximized for the catalysts based on Pd@Pt2-3L nanocubes. Because of the reduction in Pt content used and the enhancement in specific activity, the Pd@Pt1L nanocubes showed a Pt mass activity with almost three-fold enhancement relative to the Pt/C catalyst.