Center for Electrochemistry, Department of Chemistry, The University of Texas at Austin , Austin, Texas 78712, United States.
J Am Chem Soc. 2017 Dec 6;139(48):17677-17682. doi: 10.1021/jacs.7b10646. Epub 2017 Nov 21.
We describe a method for the electrodeposition of an isolated single Pt atom or small cluster, up to 9 atoms, on a bismuth ultramicroelectrode (UME). This deposition was immediately followed by electrochemical characterization via the hydrogen evolution reaction (HER) that occurs readily on the electrodeposited Pt but not on Bi. The observed voltammetric current plateau, even for a single atom, which behaves as an electrode, allows the estimation of deposit size. Pt was plated from solutions of femtomolar PtCl, which allowed precise control of the arrival of ions and thus the plating rate on the Bi UME, to one ion every few seconds. This allowed the atom-by-atom fabrication of isolated platinum deposits, ranging from single atoms to 9-atom clusters. The limiting currents in voltammetry gave the size and number of atoms of the clusters. Given the stochasticity of the plating process, we show that the number of atoms plated over a given time (10 and 20 s) follows a Poisson distribution. Taking the potential at a certain current density as a measure of the relative rate of the HER, we found that the potential shifted positively as the size increased, with single atoms showing the largest overpotentials compared to bulk Pt.
我们描述了一种在铋超微电极（UME）上电沉积单个 Pt 原子或小团簇（最多 9 个原子）的方法。这种沉积立即通过析氢反应（HER）进行电化学表征，HER 在电沉积的 Pt 上很容易发生，但在 Bi 上不会发生。即使对于单个原子（其行为类似于电极），也可以观察到稳定的伏安电流平台，从而可以估计沉积物的大小。Pt 是从纳摩尔 PtCl 溶液中沉积的，这允许精确控制离子的到达，从而控制 Bi UME 上的沉积速率，使得每几秒钟沉积一个离子。这允许逐个原子地制造孤立的铂沉积物，从单个原子到 9 个原子的团簇。伏安法中的极限电流给出了团簇的大小和原子数。考虑到电镀过程的随机性，我们表明在给定时间（10 秒和 20 秒）内沉积的原子数遵循泊松分布。我们以一定电流密度下的电位作为 HER 相对速率的度量，发现随着尺寸的增加，电位向正方向移动，与体相 Pt 相比，单个原子表现出最大的过电位。
