Ultrafast Laser Spectroelectrochemistry

在这个由化学系化学测量和成像项目资助的项目中，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，用于探测电化学转化过程中电极表面的分子。像燃料电池和电池这样的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，很难理解这些过程在单个分子的基本水平上是如何工作的。更深入的基本理解产生了电化学科学重大新进展所需的知识。研究人员制造了带有光学窗口的电池和燃料电池，并将激光束照射到电极上，以实时观察分子的行为。然而，有一个主要问题；在发生化学反应的电极上，每有一个分子，就有大约10亿个旁观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，包括用计算机脉冲激光束和控制激光波长。这使得激光束可以忽略旁观分子，这样研究人员就可以看到电化学反应器深处的化学反应是如何发生的。这项工作将对新技术的发展产生广泛的影响，这些新技术将提高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的工作，即开发电化学光谱探测仪器，使用非线性相干红外（IR）光谱方法称为和频产生（SFG）。SFG是研究埋藏界面（如埋在厚电解质层下的电极）化学的最有力的方法之一。第一项工作旨在通过克服通过红外窗口和电解质的fs红外脉冲的时间和频率畸变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用于预扭曲红外脉冲，使其不失真地到达电极。第二个努力是开发仪器来研究电极上的超快分子动力学，通过电极的超快激光温度跳变，同时探测SFG吸附的分子。在电化学电池中，一个相当小的（50 K）温度跳变可以对电极电位产生显著的影响（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.