Jayamaha Gunani, Tegg Levi, Bentley Cameron L, Kang Minkyung
School of Chemistry, The University of Sydney, Camperdown, New South Wales 2006, Australia.
School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Camperdown, New South Wales 2006, Australia.
ACS Phys Chem Au. 2024 May 10;4(4):375-384. doi: 10.1021/acsphyschemau.4c00016. eCollection 2024 Jul 24.
Conventional electrodes and electrocatalysts possess complex compositional and structural motifs that impact their overall electrochemical activity. These motifs range from defects and crystal orientation on the electrode surface to layers and composites with other electrode components, such as binders. Therefore, it is vital to identify how these individual motifs alter the electrochemical activity of the electrode. Scanning electrochemical cell microscopy (SECCM) is a powerful tool that has been developed for investigating the electrochemical properties of complex structures. An example of a complex electrode surface is Zn-Al alloys, which are utilized in various sectors ranging from cathodic protection of steel to battery electrodes. Herein, voltammetric SECCM and correlative microstructure analysis are deployed to probe the electrochemical activities of a range of microstructural features, with 651 independent voltammetric measurements made in six distinctive areas on the surface of a Zn-Al alloy. Energy-dispersive X-ray spectroscopy (EDS) mapping reveals that specific phases of the alloy structure, particularly the α-phase Zn-Al, favor the early stages of metal dissolution (i.e., oxidation) and electrochemical reduction processes such as the oxygen reduction reaction (ORR) and redeposition of dissolved metal ions. A correlative analysis performed by comparing high-resolution quantitative elemental composition (i.e., EDS) with the corresponding spatially resolved cyclic voltammograms (i.e., SECCM) shows that the nanospot α-phase of the Zn-Al alloy contains high Al content (30-50%), which may facilitate local Al dissolution as the local pH increases during the ORR in unbuffered aqueous media. Overall, SECCM-based high-throughput electrochemical screening, combined with microstructure analysis, conclusively demonstrates that structure-composition heterogeneity significantly influences the local electrochemical activity on complex electrode surfaces. These insights are invaluable for the rational design of advanced electromaterials.
传统电极和电催化剂具有复杂的组成和结构模式，这些模式会影响它们的整体电化学活性。这些模式范围从电极表面的缺陷和晶体取向到与其他电极组件（如粘合剂）的层和复合材料。因此，确定这些个体模式如何改变电极的电化学活性至关重要。扫描电化学池显微镜（SECCM）是一种强大的工具，已被开发用于研究复杂结构的电化学性质。复杂电极表面的一个例子是锌铝合金，它被应用于从钢铁的阴极保护到电池电极等各个领域。在此，采用伏安SECCM和相关微观结构分析来探测一系列微观结构特征的电化学活性，在锌铝合金表面的六个不同区域进行了651次独立的伏安测量。能量色散X射线光谱（EDS）映射显示，合金结构的特定相，特别是α相锌铝，有利于金属溶解（即氧化）的早期阶段以及诸如氧还原反应（ORR）和溶解金属离子再沉积等电化学还原过程。通过将高分辨率定量元素组成（即EDS）与相应的空间分辨循环伏安图（即SECCM）进行比较所进行的相关分析表明，锌铝合金的纳米点α相含有高铝含量（30 - 50%），这可能在未缓冲的水性介质中ORR期间随着局部pH值的增加促进局部铝的溶解。总体而言，基于SECCM的高通量电化学筛选与微观结构分析相结合，最终证明结构 - 组成异质性显著影响复杂电极表面的局部电化学活性。这些见解对于先进电子材料的合理设计具有重要价值。
