Scanning Electrochemical Microscopy and Ultramicroelectrode Studies of Electrocatalysis at Nanoparticle Ensembles of Microdimensions and at Single Nanoparticles

在这个由化学系化学测量和成像项目资助的项目中，新墨西哥州立大学的Cynthia Zoski教授正在研究有限纳米粒子集合和单纳米粒子在超微观尺寸导电表面上的电催化，在高质量传输条件下进行动力学研究。纳米颗粒是燃料和太阳能电池等能源设备中催化剂整体设计的重要组成部分。这些研究提供了纳米颗粒大小、分布和催化活性之间关系的广泛知识。这些研究还解决了电催化中的一个关键问题，即电极反应发生时催化剂表面上的中间体和吸附物质的性质，这有助于诊断反应机制，与分子识别、传感和感染性疾病相关，其中生物膜完整性以及与群体感应和细菌微菌落的关系令人感兴趣。更广泛的影响还包括培养在国家重要领域从事多学科科学研究的博士后和研究生，以及开发一门新的高级电化学技术课程，面向化学、化学工程、物理和生物学领域的博士后、研究生和大四本科生。该项目侧重于纳米粒子集成和单纳米粒子的电催化，发展模拟来描述它们的行为，通过在超微电极上的单纳米粒子碰撞来制造和分析集成和单纳米粒子电极，以及使用扫描电化学显微镜来研究电生成氧化膜和电催化反应吸附的氧化膜的动力学和反应性的本质。纳米颗粒电极的碰撞方法允许控制表面上纳米颗粒的数量，选择电极材料和纳米颗粒类型（例如金属，核壳，合金）和尺寸的灵活性，以及在同一电极上直接比较有限系综和单个纳米颗粒动力学。碰撞瞬态的形状提供了对纳米颗粒与电极相互作用性质的微观细节的洞察，以及电催化反应的动力学，如单个纳米颗粒的氧还原。利用瞬态表面询问扫描电化学显微镜来研究氧化膜的性质和反应性，克服了传统电化学实验中使用工作电极本身寻找中间体以及响应与电解和电容电荷产生的电流相混淆的困难。

In this project funded by the Chemical Measurement and Imaging Program of the Division of Chemistry, Professor Cynthia Zoski of New Mexico State University is studying electrocatalysis at finite nanoparticle ensembles and single nanoparticles on conducting surfaces of ultramicrodimensions where kinetic investigations are carried out under high mass transport conditions. Nanoparticles are an important part of the overall catalyst design in energy devices such as fuel and solar cells. These studies provide wide-ranging knowledge on the relationship between nanoparticle size, distribution, and catalytic activity. These studies also address a key issue in electrocatalysis regarding the nature of intermediates and adsorbed species on a catalyst surface while the electrode reaction occurs, which aid in diagnosis of reaction mechanisms, with relevance to molecular recognition, sensing, and to infectious diseases where biofilm integrity and the relationship to quorum sensing and bacteria micro-colonies are of interest. Broader impacts also include training of post-doctoral fellows and graduate students in multi-disciplinary scientific research in areas of national importance, and developing a new course in advanced electrochemical techniques which targets post-doctoral fellows, graduate and senior undergraduate students from chemistry, chemical engineering, physics, and biology.This project focuses on electrocatalysis at nanoparticle ensembles and single nanoparticles, development of simulations to describe their behavior, fabrication and analysis of ensemble and single nanoparticle electrodes through single nanoparticle collisions at ultramicroelectrodes, and the use of scanning electrochemical microscopy to study the kinetics and nature of the reactivity of electrogenerated oxide films and those adsorbed as a result of an electrocatalytic reaction. The collision approach to nanoparticle electrodes allows control over the number of nanoparticles on a surface, flexibility in selection of the electrode material and nanoparticle type (e.g. metallic, core shell, alloy) and size, and a direct comparison between finite ensemble and single nanoparticle kinetics at the same electrode. The shape of collision transients provides insight into the microscopic details of the nature of nanoparticle interaction with an electrode and the kinetics of electrocatalytic reactions such as oxygen reduction at single nanoparticles. Using transient surface interrogation scanning electrochemical microscopy to study the nature and reactivity of oxide films overcomes the difficulties in traditional electrochemical experiments where the working electrode itself is used to find intermediates and the response is convoluted with the current from the electrolysis and capacitive charge.