Electrochemical stability of nanometer-scale Pt particles in acidic environments.
Electrochemical stability of nanometer-scale Pt particles in acidic environments.
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DOI：
10.1021/ja9071496
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发表时间：
2010-01
影响因子：
15
通讯作者：
Lei Tang;Byungchan Han;K. Persson;C. Friesen;T. He;K. Sieradzki;G. Ceder
中科院分区：
文献类型：
--
作者：
Lei Tang;Byungchan Han;K. Persson;C. Friesen;T. He;K. Sieradzki;G. Ceder
了解和控制纳米级固体的电化学稳定性或腐蚀行为在纳米级电子学、传感和催化等各种应用中至关重要。对于许多应用，通过减小颗粒尺寸实现的增加的表面与体积比导致更低的材料成本和更高的效率，但是存在关于材料的固有稳定性是否也随着颗粒尺寸而降低的问题。这方面的一个重要实例涉及Pt催化剂在例如质子交换燃料电池中的稳定性。在这篇文章中，我们使用电化学扫描隧道显微镜，第一次，直接检查单个Pt纳米粒子的稳定性作为施加电位的函数。我们结合联合收割机的实验研究与从头计算，以确定的稳定性，钝化和溶解行为的Pt作为一个功能的颗粒大小和潜力。这两种方法都清楚地表明，较小的Pt颗粒溶解远低于本体溶解电位，并通过不同的机制。Pt从纳米颗粒中溶解是通过Pt直接电氧化成可溶性Pt（2+）阳离子而发生的，这与从氧化物中溶解的本体Pt不同。这些结果对于理解燃料电池结构中Pt和Pt合金催化剂的稳定性以及纳米颗粒的稳定性具有重要意义。
Understanding and controlling the electrochemical stability or corrosion behavior of nanometer-scale solids is vitally important in a variety of applications such as nanoscale electronics, sensing, and catalysis. For many applications, the increased surface to volume ratio achieved by particle size reduction leads to lower materials cost and higher efficiency, but there are questions as to whether the intrinsic stability of materials also decreases with particle size. An important example of this relates to the stability of Pt catalysts in, for example, proton exchange fuel cells. In this Article, we use electrochemical scanning tunneling microscopy to, for the first time, directly examine the stability of individual Pt nanoparticles as a function of applied potential. We combine this experimental study with ab initio computations to determine the stability, passivation, and dissolution behavior of Pt as a function of particle size and potential. Both approaches clearly show that smaller Pt particles dissolve well below the bulk dissolution potential and through a different mechanism. Pt dissolution from a nanoparticle occurs by direct electro-oxidation of Pt to soluble Pt(2+) cations, unlike bulk Pt, which dissolves from the oxide. These results have important implications for understanding the stability of Pt and Pt alloy catalysts in fuel cell architectures, and for the stability of nanoparticles in general.