Infrared Spectroscopic imaging of reactions at solid-liquid interfaces

该项目旨在利用红外光谱技术对溶液中固体表面二维传播的化学反应进行成像。与传统的光学显微镜不同，通过绘制分子振动特征的强度或频率，可以对参与反应的化学物质的二维分布进行成像。为了实现红外成像，使用了64 × 64多通道MCT探测器（焦平面分析仪，FPA）。我们感兴趣的目标是吸附单层的快速反应，本方法的实验难点是非常低的红外吸收。为了解决这一问题，本实验室开发了表面增强红外吸收光谱（SEIRAS）。经过巨大的努力，我们已经成功地成像CO吸附在Pt电极（包括图案电极）上的空间分布，并证明了这种方法的实用性。然而，由于图像的低信噪比和FT-IR光谱仪到控制计算机的数据传输速率慢（一张图像的数据大小为几GB），我们还没有成功地监测在恒流或恒电位甲酸电氧化下预计形成的空间和时间振荡模式。这个问题将在将来通过改进光谱仪的电子设备来解决。同时，我们还研究了电化学界面上几种催化反应的机理，如Pt和Ag上的析氢反应，小有机分子（CO、甲醇、甲醛、甲酸和二甲基醚）的电氧化反应。在这一系列的研究中，最显著的成就是小有机分子的电氧化是通过吸附在表面的甲酸物质发生的。用红外光谱对各反应机理进行了详细分析。

This project aimed to image chemical reactions that propagate two dimensionally over solid surfaces in solution by using infrared spectroscopy. Different from conventional optical microscope, two dimensional distributions of chemical species involved in the reactions can be imaged by plotting the intensity or frequency of a molecular vibration characteristic to each species. To realize the IR imaging, a 64 x 64 multi-channel MCT detector (Focal Plane Analyzer, FPA) was used. The target we have interested in is fast reactions of adsorbed monolayers and an experimental difficulty of the present approach is the very low IR absorption. To overcome this problem, surface-enhanced infrared absorption spectroscopy (SEIRAS) developed in this laboratory was couple. After great efforts, we have succeeded in imaging the spatial distribution of CO adsorbed on Pt electrodes (including patterned electrodes) and demonstrated the usefulness of this approach. However, we have not yet succeeded in monitoring spatially and temporally oscillating patterns that are expected to be formed under galvanostatic or potentiostatic electro-oxidation of formic acid due to the low signal-to-noise ratio of the image and the slow data transfer rate from the FT-IR spectrometer to the controlling computer (the data size of one image is a few GB). This problem will be removed in future by modifying the electronics of the spectrometer.In parallel, we investigated the mechanisms of several catalytic reactions at the electrochemical interface, such as hydrogen evolution reaction on Pt and Ag, electro-oxidation of small organic molecules (CO, methanol, formaldehyde, formic acid, and dimethyl eter). The most notable achievement in this series of study is that electrooxidation of small organic molecules occurs through formate species adsorbed on the surface. The mechanism of each reaction was examined in detail by IR spectroscopy.