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激光仪器，可在电化学转化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是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如何工作。更深入的基础理解可以产生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，并向电极照射激光束以实时观察分子的行为。但有一个大问题；对于发生化学反应的电极上的每个分子，大约有十亿个旁观分子没有做任何感兴趣的事情。为了解决这个问题，研究人员正在开发涉及脉冲激光束并通过计算机控制激光波长的方法。这使得激光束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深处的化学反应是如何发生的。这项工作将对新技术的开发产生广泛的影响，从而提高燃料电池和电池等设备的性能。通过让研究生和本科生参与科学研究，它对下一代科学家的培训产生了更广泛的影响。该项目由两项相关工作组成，旨在开发使用非线性相干红外（IR）光谱方法（称为和频生成（SFG））进行电化学光谱探测的仪器。 SFG 是研究埋入界面化学的最强大方法之一，例如埋在厚电解质层下的电极。第一项努力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失真来提高在掩埋界面处获取 SFG 光谱的能力。计算机控制的红外脉冲整形技术用于对红外脉冲进行预失真，使其到达电极时不失真。第二项努力旨在开发仪器，通过电极的超快激光温度跳跃来研究电极上的超快分子动力学，同时通过 SFG 探测吸附的分子。在电化学电池中，相当小的 (50 K) 温度跃变会对电极电位产生显着影响 (100 mV)。温度跳跃方法是一种快速（以纳秒为单位）跳跃电极电势的方法，其速度远快于电气方法。

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.