Bentley Cameron L, Unwin Patrick R
Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK.
Faraday Discuss. 2018 Oct 1;210(0):365-379. doi: 10.1039/c8fd00028j.
Techniques in the scanning electrochemical probe microscopy (SEPM) family have shown great promise for resolving nanoscale structure-function (e.g., catalytic activity) at complex (electro)chemical interfaces, which is a long-term aspiration in (electro)materials science. In this work, we explore how a simple meniscus imaging probe, based on an easily-fabricated, single-channeled nanopipette (inner diameter ≈ 30 nm) can be deployed in the scanning electrochemical cell microscopy (SECCM) platform as a fast, versatile and robust method for the direct, synchronous electrochemical/topographical imaging of electrocatalytic materials at the nanoscale. Topographical and voltammetric data are acquired synchronously at a spatial resolution of 50 nm to construct maps that resolve particular surface features on the sub-10 nm scale and create electrochemical activity movies composed of hundreds of potential-resolved images on the minutes timescale. Using the hydrogen evolution reaction (HER) at molybdenite (MoS2) as an exemplar system, the experimental parameters critical to achieving a robust scanning protocol (e.g., approach voltage, reference potential calibration) with high resolution (e.g., hopping distance) and optimal scan times (e.g., voltammetric scan rate, approach rate etc.) are considered and discussed. Furthermore, sub-nanoentity reactivity mapping is demonstrated with glassy carbon (GC) supported single-crystalline {111}-oriented two-dimensional Au nanocrystals (AuNCs), which exhibit uniform catalytic activity at the single-entity and sub-single entity level. The approach outlined herein signposts a future in (electro)materials science in which the activity of electroactive nanomaterials can be viewed directly and related to structure through electrochemical movies, revealing active sites unambiguously.
扫描电化学探针显微镜（SEPM）家族中的技术已显示出在解析复杂（电）化学界面处的纳米级结构-功能（如催化活性）方面具有巨大潜力，这是（电）材料科学中的一个长期目标。在这项工作中，我们探索了一种基于易于制造的单通道纳米移液器（内径≈30 nm）的简单弯月面成像探针如何能够部署在扫描电化学池显微镜（SECCM）平台中，作为一种快速、通用且强大的方法，用于在纳米尺度上对电催化材料进行直接、同步的电化学/形貌成像。以50 nm的空间分辨率同步采集形貌和伏安数据，以构建能够解析亚10 nm尺度上特定表面特征的图谱，并创建由数百个在分钟时间尺度上的电位分辨图像组成的电化学活性电影。以辉钼矿（MoS2）上的析氢反应（HER）为例，考虑并讨论了对于实现具有高分辨率（如跳跃距离）和最佳扫描时间（如伏安扫描速率、接近速率等）的稳健扫描协议至关重要的实验参数（如接近电压、参比电位校准）。此外，使用玻璃碳（GC）负载的单晶{111}取向二维金纳米晶体（AuNCs）展示了亚纳米实体反应性映射，这些纳米晶体在单实体和亚单实体水平上表现出均匀的催化活性。本文概述的方法为（电）材料科学指明了一个未来方向，即在这个方向中，可以通过电化学电影直接观察电活性纳米材料的活性，并将其与结构相关联，明确揭示活性位点。
