Dynamics at Electrode-Electrolyte Interfaces Down to the Nanosecond Domain

该项目由化学测量和成像计划以及化学结构，动力学和机制- A计划共同资助。两人都是化学系的。凯斯西储大学的丹尼尔·谢尔森教授正在开发和使用硬件和电分析方法，用于在电极/电解质界面上进行超快电荷注入。这种能力使电化学现象的基础研究的时间尺度下降到纳秒（ns）制度。这些新的超快电子学与光谱技术相结合，如二次谐波产生（SHG），和频产生（SFG）和差分反射光谱。这项工作将提供的手段来回答有关短寿命的吸附物和活性中间体的动力学的基本问题。电极和电解质界面的行为与广泛的电化学应用高度相关。电化学表面科学是化学、物理和许多工程领域如材料和电子学的结合点。科学进步将影响广泛的具有实际意义的领域，如能源转换、缓蚀和传感器技术。在这一领域进行研究的学生接触到非常广泛的基础和应用学科。这种类型的培训将使学生特别适合面对环境修复，能源转换，能源储存，生物科学和微传感器技术中许多重要和未解决的问题所带来的挑战。这项工作的主要目标是开发和实施实验技术，以实现在纳秒制度的电极/电解质界面的电位控制，并监测随后的时间演变的接口使用光谱技术具有最高的灵敏度和特异性和时间分辨率。注意力集中在超快电荷注入策略，采用电子电路和电化学电池架构设计与泰克（吉时利）。这些都是使用选定的模型系统，涉及定义明确的单晶金属基板和吸附层进行验证。使用线性和非线性光谱探针监测系统对这种快速电扰动的响应，包括归一化差分反射率和二次谐波（SHG）以及和频产生（SFG）。研究的实际模型系统包括：带有氧化还原活性端基的自组装单层中的电子转移作为离电极表面的距离的函数，单晶银上卤化物吸附物层中的有序/无序转变，和Pt（111）上的氢吸附/脱附还探索了使用施加到溶液的超快电流脉冲，以调节界面上的静电势，从而调节溶液的pH。超电势驱动界面事件。预计从这项研究中得到的实验数据将用于验证界面动力学快速发展领域的理论预测。该奖项反映了NSF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。

This project is jointly funded by the Chemical Measurement and Imaging Program and the Chemical Structure, Dynamics and Mechanisms - A Program. Both are in the Division of Chemistry. Professor Daniel Scherson of Case Western Reserve University is developing and using hardware and electroanalytical methods for ultrafast charge injection across electrode/electrolyte interfaces. This capability enables fundamental studies of electrochemical phenomena at timescales down to the nanosecond (ns) regime. These new ultrafast electronics are combined with spectroscopic techniques such as second harmonic generation (SHG), sum frequency generation (SFG), and differential reflectance spectroscopy. This work will provide the means to answer fundamental questions about the dynamics of short-lived adsorbates and reactive intermediates. The behavior of electrode and electrolyte interfaces are highly relevant to a wide-range of electrochemical applications. Electrochemical surface science lies at the juncture of chemistry, physics and a wide number of engineering fields, such as materials and electronics. The scientific advances will impact wide ranging areas of practical importance such as energy conversion, corrosion mitigation and sensor technology. Students pursuing research in this area become exposed to a very broad range of both fundamental and applied disciplines. This type of training will produce students especially suited to face the challenges posed by a multitude of important and unresolved problems in environmental remediation, energy conversion, energy storage, biosciences, and microsensor technology. The primary objectives of this work are to develop and implement experimental techniques to achieve potential control across electrode/electrolyte interfaces in the nanosecond regime, and to monitor the subsequent time evolution of the interface using spectroscopic techniques with the highest sensitivity and specificity and temporal resolution. Attention is focused on ultrafast charge injection tactics employing electronic circuitry and electrochemical cell architectures designed in collaboration with Tektronix (Keithley). These is validated using selected model systems involving both well-defined single crystal metal substrates and adsorbate layers. The response of the systems to such fast electrical perturbations is monitored using linear and non-linear spectroscopic probes, including normalized differential reflectance, and second harmonic, (SHG) and sum frequency generation (SFG). The actual model systems investigated include: electron transfer in self-assembled monolayers bearing redox active terminal groups as a function of the distance from the electrode surface, order/disorder transitions in halide adsorbate layers on single crystal silver, and hydrogen adsorption/desorption on Pt(111) as a function of pH. Also explored is the use of ultrafast current pulses applied to the solution in order to modulate the electrostatic potential across the interface and thus the overpotential driving the interfacial events. It is expected that the experimental data resulting from this research will serve to validate theoretical predictions emerging from the fast developing field of interfacial dynamics.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.