High Throughput Atom-by-Atom Electrochemistry

电化学有着悠久的历史，但从未像今天这样重要，是最令人兴奋的科学分支之一。电化学是电池、燃料电池和太阳能电池中能量储存和利用技术的核心。它在传感和诊断平台中的应用正在扩大，并为纳米材料，功能化表面和电合成的创造提供了新的可能性。这些技术的出现是因为好奇的科学。一个著名的例子是Volta在两个多世纪前开发的电池，不是作为能量储存和利用的手段，而是为了反驳Galvani关于“动物电”起源的论点。然而，如果没有电池，我们今天会在哪里？基本的电化学过程是非常具有挑战性的研究，并受到传统的实验能力，这往往集中在宏观（应用）世界或（最好的，但很少）中尺度的限制。我们打算制造并证明最小的可能电极：一个单独的单原子，由单个离子的电还原产生。我们将确定该过程发生的条件，并研究所得单原子电极上的电化学过程。这一雄心勃勃的目标将通过结合纳米电化学和成像科学的最新发展来实现。我们将使用纳米级移液管探针在扫描电化学电池显微镜（SECCM）格式，以可控的方式提供金属离子的一系列微小区域的硼掺杂金刚石透射电子显微镜（TEM）网格，这将作为一个电极，以减少碰撞离子原子。然后通过像差校正扫描透射电子显微镜（ac-STEM）分析该网格。我们将进一步探索和证明一个自下而上的方法，生产纳米团簇原子原子。我们将研究这些单原子和少原子电极的电催化过程，以了解电化学过程如何从最小的尺寸向上扩展。所提出的方法的美妙之处在于，在通过SECCM在一个点中进行电沉积之后，纳米移液管被撤回，横向平移一小段距离并降落在新鲜的新点中用于下一次电沉积，在重复以创建扫描阵列的过程中，通常在合理的时间尺度上具有数千个单独的点。因此，将有可能在实验运行中执行数千个实验（试验），这将允许ac-STEM在一个扫描实验中探索和分析宽的参数空间。这种独特的高通量组合显微镜方法对于获得固有随机过程的统计数据并提供实验结果的直接证明至关重要。(i)单个原子的沉积。我们将研究电沉积的条件下，平均结果是一个单一的原子在一个表面上，由单分子扩散的随机性质的限制。(ii)金属纳米结构和团簇的原子-原子组装。我们的研究将提供前所未有的洞察成核和生长过程一般，在最早的阶段，以前无法访问的调查。(iii)电化学测量将揭示在单个原子尺度的电催化实体的电极动力学，并在此规模的质量传输和双层效应的见解。(iv)如果时间允许，我们将研究是否有可能制造单个的纳米合金（只有两个或几个原子）。我们的工作将实验电化学带到了一个新的领域：原子长度尺度和纳米尺度时间尺度。

Electrochemistry has a long history, but has never been more important than today, and is one of the most exciting branches of science. Electrochemistry is at the centre of energy storage and utilisation technologies, in batteries, fuel cells and solar cells. It is finding expanding applications in sensing and diagnostic platforms, and presenting new possibilities for the creation of nanomaterials, functionalised surfaces and in electrosynthesis. These technologies have emerged because of inquisitive science. A famous example is the development of the battery by Volta more than two centuries ago, not as a means of energy storage and utilisation, but to counter an argument with Galvani about the origin of "animal electricity". Yet, where would we be today without the battery?Fundamental elementary electrochemical processes are extremely challenging to study and are limited by conventional experimental capability, which tends to focus on the macroscopic (applications) world or (at best, but rare) mesoscale. We intend to make and prove the smallest possible electrode: an individual single atom, produced by the electro-reduction of a single ion. We shall determine the conditions whereby this process occurs and study electrochemical processes at the resulting single atom electrode. This ambitious goal will be achieved by marrying recent developments in nanoscale electrochemistry and imaging science. We shall use nanoscale pipette probes in a scanning electrochemical cell microscopy (SECCM) format to deliver metal ions in a controllable way to a series of tiny regions on a boron doped diamond transmission electron microscopy (TEM) grid, which will serve as an electrode to reduce the impinging ions to atoms. This grid will then be analysed by aberration corrected-scanning transmission electron microscopy (ac-STEM). We shall further explore and prove a bottom-up approach for the production of nanoclusters atom-by-atom. We shall investigate electrocatalytic processes at these single atom and few-atom electrodes, to understand how electrochemical processes scale from the smallest possible size upwards. The beauty of the proposed approach is that after electrodeposition in one spot by SECCM, the nanopipette is withdrawn, translated laterally by a small distance and landed in a fresh, new spot for the next electrodeposition, in a process that is repeated to create a scanned array, typically of several thousand individual spots on a reasonable timescale. Thus, it will be possible to execute several thousand experiments (trials) in an experimental run that will allow a wide parameter space to be explored and analysed by ac-STEM in one scan experiment. This unique high throughput combinatorial microscopy approach is crucial for obtaining statistics on an inherently stochastic process and to provide direct proof of the experimental outcome. (i) Deposition of single atoms. We shall study electrodeposition under conditions where the average outcome is a single atom on a surface, bounded by the limits of the stochastic nature of single molecule diffusion. (ii) Atom-by-atom assembly of metal nanostructures and clusters. Our studies will provide unprecedented insight into nucleation and growth processes generally, at the very earliest stages, not previously accessible to investigation.(iii) Electrochemical measurements will reveal electrode kinetics at individual atom scale electrocatalytic entities, and also insights on mass transport and double layer effects at this scale. (iv) If time permits, we shall investigate whether it is possible to make individual bimetallic nano-alloys (of just 2 or few atoms). Our work takes experimental electrochemistry to a new domain: the atom lengthscale and nanoscale timescale.