Ultrafast Laser Spectroelectrochemistry

在这个由化学系化学测量和成像计划资助的项目中，伊利诺伊大学的Dana Dlott教授正在开发先进的基于激光的仪器，在电化学转换过程中探测电极表面的分子。燃料电池和电池等电化学系统构成了我们工业经济的重要组成部分，但事实证明，很难理解这些过程如何在单个分子的基本水平上工作。更深层次的基础性理解产生了电化学科学取得重大新进展所需的知识。研究人员建造了带有光学窗口的电池和燃料电池，并将激光照射到电极上，以实时观察分子的行为。然而，有一个大问题：对于发生化学反应的电极上的每个分子，大约有10亿个旁观者分子不做任何感兴趣的事情。为了解决这个问题，研究人员正在开发一种方法，包括对激光光束进行脉冲处理，并由计算机控制激光波长。这使得激光可以忽略旁观者分子，这样研究人员就可以看到电化学反应器内部的化学作用是如何发生的。这项工作将对新技术的开发产生广泛影响，这些新技术将增强燃料电池和电池等设备的性能。它通过让研究生和本科生参与科学研究，对培养下一代科学家产生了进一步广泛的影响。该项目包括两项相关工作，即利用一种称为和频产生(SFG)的非线性相干红外光谱学方法开发电化学光谱探测仪器。SFG是研究埋藏界面化学的最有效方法之一，例如埋在厚电解液层下的电极。第一项工作旨在通过克服飞秒红外脉冲通过红外窗口和电解液的时间和频率失真来提高在埋藏界面获得SFG光谱的能力。计算机控制的红外脉冲整形技术被用来预失真红外脉冲，使其不失真地到达电极。第二项工作旨在开发研究电极上超快分子动力学的仪器，方法是在用SFG探测吸附分子的同时，使电极发生超快激光温度跳跃。在电化学电池中，相当小的(50K)温度跃升可以对电极电位产生重大影响(100 MV)。温度跳跃法是一种快速(以纳秒为单位)跳跃电极电位的方法，其速度远远快于电学方法。

In this project funded by the Chemical Measurement and Imaging program in the Division of Chemistry, Prof. Dana Dlott of the University of Illinois is developing advanced laser-based instruments that probe molecules on the surfaces of electrodes during electrochemical transformations. Electrochemical systems such as fuel cells and batteries form a significant part of our industrial economy, yet it has proven difficult to understand how these processes work at the fundamental level of individual molecules. A deeper fundamental understanding produces the knowledge needed for major new advances in electrochemical sciences. The investigators build batteries and fuel cells with optical windows, and shine laser beams at the electrodes to watch how the molecules behave in real time. There is a major problem, though; for every molecule at the electrode where the chemistry takes place, there are about one billion spectator molecules not doing anything of interest. To address this problem, the investigators are developing methods that involve pulsing the laser beams and controlling the laser wavelengths by computers. This allows the laser beams to ignore the spectator molecules so the researchers can see how chemistry takes place deep inside electrochemical reactors. The work will have a broad impact on the development of new technologies that will enhance the performance of devices such as fuel cells and batteries. It is having a further broad impact on the training of the next generation of scientists, by involving students at the graduate and undergraduate level in scientific research. The project consists of two related efforts to develop instruments for spectroscopic probing of electrochemistry using a nonlinear coherent infrared (IR) spectroscopy method termed sum-frequency generation (SFG). SFG is one of the most powerful methods to study chemistry at buried interfaces such as electrodes buried under thick electrolyte layers. The first effort seeks to improve the ability to obtain SFG spectra at buried interfaces by overcoming temporal and frequency distortions of fs IR pulses passing through an IR window and an electrolyte. Computer-controlled IR pulse-shaping techniques are used to predistort the IR pulses so they arrive undistorted at the electrodes. The second effort seeks to develop instruments to study ultrafast molecular dynamics at electrodes by ultrafast laser temperature jumping of the electrodes while probing the adsorbed molecules by SFG. In an electrochemical cell, a rather small (50 K) temperature jump can have a significant effect (100 mV) on the electrode potential. The temperature-jump method is a way to rapidly (in nanoseconds) jump electrode potentials far faster than is possible by electrical methods.