Chemical Imaging of Metal Surfaces at the Solid-Liquid Interface: Effects of Grain Structure on Electrocatalytic Reactions

在化学结构，动力学和机理- a （CSDM-A）和化学测量和成像（CMI）项目的支持下，休斯顿大学的Steven Baldelli教授正在使用高灵敏度的表面技术来了解分子如何在多晶电极上反应。被电极吸附的分析物的化学反应性取决于表面及其邻近颗粒的结晶度。研究这些效应需要使用揭示表面晶体学的方法，依赖于电极表面电子状态和对称性，以及影响吸附分子的局部振动信息。通过电化学控制系统，Baldelli教授和他的学生将绘制表面化学图，并将其与潜在的晶体学联系起来，以发展对晶体域如何影响多相催化的物理理解。研究生、本科生和高中生将通过这项研究得到指导和合作。学生将发展与仪器制造、数据分析、光谱和显微镜图像解释相关的技能。该项目使用原位和频率产生振动光谱/显微镜（SFG）来探测吸附在电极上的分子，而二次谐波产生显微镜（SHG）有助于确定电极的电子状态和对称性。由于SHG各向异性与表面晶体学有关，因此这些技术的结合可以生成表面化学和底层晶体学的相关图。然后在反应条件下使用亚微米分辨率的循环伏安法检测表面反应性。通过这样做，可以评估多晶表面中相邻晶粒的影响。这项工作的广泛影响有可能推动表面敏感光谱和显微镜工具的发展，这些工具可以促进对电极如何影响多相电催化的化学和物理理解。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) and the Chemical Measurement and Imaging (CMI) Programs in the Division of Chemistry, Professor Steven Baldelli from the University of Houston is using highly sensitive surface techniques to understand how molecules react on polycrystalline electrodes. Chemical reactivity of analytes adsorbed to an electrode depends on the underlying crystallinity of a surface as well as its adjacent grains. Studying these effects require the use of methods that reveal surface crystallography, depend on the electrode surface electronic state and symmetry, and impact local vibrational information about the adsorbed molecules. By controlling the system electrochemically, Professor Baldelli and his students will map surface chemistry and link it to underlying crystallography to develop a physical understanding of how crystalline domains influence heterogeneous catalysis. Graduate, undergraduate, and high school students will be mentored and collaborate through this research. Students will develop skills related to instrument building, data analysis, and spectral and microscopy image interpretation.This project uses in situ sum frequency generation vibrational spectroscopy/microscopy (SFG) to probe molecules adsorbed to an electrode while second harmonic generation microscopy (SHG) assists in the determination of the electronic state and symmetry of the electrode. Because SHG anisotropy is related to surface crystallography, the combination of these techniques results in the generation of correlated maps of surface chemistry and underlying crystallography. Surface reactivity is then interrogated using cyclic voltammetry with sub-micron resolution under reaction conditions. In so doing, impacts of adjacent grains in a polycrystalline surface are evaluated. Broader impacts of this work have the potential to advance surface sensitive spectroscopy and microscopy tools that could advance the chemical and physical understanding of how the electrode influences heterogeneous electrocatalysis.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.