Center for Electrochemistry, Department of Chemistry , The University of Texas at Austin , Austin , Texas 78712 , United States.
J Am Chem Soc. 2019 May 8;141(18):7327-7332. doi: 10.1021/jacs.8b13366. Epub 2019 Apr 24.
We report the catalytic activity of a single, isolated Pt deposit on Bi and Pb supports to probe the size and substrate effects on the electrochemical hydrogen evolution reaction (HER). Deposits were made electrolytically by an atom-by-atom method in a controlled plating; we prepared an individual Pt deposit on Bi and Pb ultramicroelectrodes (UMEs) such as a single isolated atom, clusters containing one to five Pt atoms, and nanoparticles to about 10 nm radius. A steady-state voltammogram on the single Pt deposits is observed by electrocatalytic amplification of the HER, with a negligible contribution by the HER at the substrate UME. A single Pt atom can act as an electrode for the HER, showing a diffusion-limiting current plateau in the voltammogram that can be used to estimate the radius of a single deposit. We simulated the voltammograms of the individual deposits, assuming the Volmer step of the HER is appropriate for a Pt cluster deposit, to obtain kinetic parameters for each deposit. The HER kinetics increases as the particle radius increases from ∼0.2 to ∼4 nm for Bi and Pb substrates and then reaches a limiting plateau. The limiting kinetics on the Bi substrate approaches that of bulk Pt while that on the Pb substrate is much smaller.
我们报告了单个 Pt 沉积物在 Bi 和 Pb 载体上的催化活性，以探究尺寸和衬底对电化学析氢反应（HER）的影响。沉积物通过原子逐层的方法在受控电镀中进行电解制备；我们在 Bi 和 Pb 超微电极（UME）上制备了单个孤立的 Pt 沉积物，如单个孤立的原子、含有一到五个 Pt 原子的团簇以及约 10nm 半径的纳米颗粒。通过 HER 的电催化放大观察到单个 Pt 沉积物的稳态伏安图，其中基底 UME 的 HER 贡献可以忽略不计。单个 Pt 原子可以作为 HER 的电极，在伏安图中显示出扩散限制的电流平台，可用于估计单个沉积物的半径。我们模拟了单个沉积物的伏安图，假设 HER 的 Volmer 步骤适用于 Pt 团簇沉积物，以获得每个沉积物的动力学参数。对于 Bi 和 Pb 衬底，HER 动力学随着颗粒半径从约 0.2nm 增加到约 4nm 而增加，然后达到一个限制平台。Bi 衬底上的限制动力学接近体相 Pt，而 Pb 衬底上的限制动力学要小得多。
