SusChEM: Studying Catalysts and Reaction Intermediates for Water Oxidation by Spectroscopy of Cryogenic Mass-Selected Ions

凭借化学结构，动力学和机制A计划的这一奖项，位于博尔德的科罗拉多大学的Mathias Weber开发了一种新的实验方法来研究太阳能转换反应堆中发生的化学反应。正在研究的反应器类型利用含有钌或铜的催化剂分子将水分子分解为氢和氧。因此，来自阳光的能量被用来从水中提取可持续的燃料来源，但它的确切工作方式尚未完全了解。这种认识的缺乏阻碍了这一重要工艺过程的催化剂和反应器的设计和改进。在对这个系统的研究中，一个复杂的因素是水本身的存在。目前的研究正在通过去除太阳能反应堆中产生的分子并将其置于真空中来解决这个问题。然后可以使用高度复杂的设备来研究这些化学物质的详细性质。在真空中进行的测量将提供特征，这些特征可以在以后用于识别存在水时的那些物质，换句话说，在反应堆中，因为它正常工作。这项工作解决了一个重要的社会问题，即开发不依赖碳基燃料的替代能源。培养下一代科学家是该项目的一个组成部分。在这个项目中，研究人员正在研究选定的钌基和铜基水氧化催化剂的电子和几何结构，以及催化转化过程中出现的某些反应中间体。通过电喷雾电离将催化剂和反应中间体的离子转移到气相中。然后，离子在离子阱中冷却，质量选择，并通过脉冲光照射，该脉冲光在整个中红外，可见光和近紫外光谱中可调。通过目标离子的光致碎裂来监测光子吸收，从而允许测量它们的振动和电子光谱。 将离子冷却到低温对于获得必要的光谱细节至关重要。振动光谱将导致在研究中的离子的结构信息，这是特别重要的反应中间体。测量催化剂和反应中间体的电子光谱将有助于澄清反应溶液中的形态。此外，激发态振动结构有助于研究人员对激发态动力学和反应性进行计算建模研究。

With this award from the Chemical Structure, Dynamics and Mechanisms A program, Mathias Weber of the University of Colorado at Boulder develops a new experimental approach to study chemical reactions that occur in a solar energy conversion reactor. The type of reactor being studied utilizes a catalyst molecule that contains either ruthenium or copper to split water molecules into hydrogen and oxygen. Energy from sunlight is, thus, used to extract a sustainable source of fuel from water, but the precise way it works is not fully understood. This lack of understanding hinders the design and improvement of catalysts and reactors for this important technological process. One of the complicating factors in studies of this system is the presence of the water itself. The current research is getting around this problem by removing the molecules produced in the solar reactor and putting them into a vacuum. Highly sophisticated pieces of equipment can then be used to study the detailed nature of these chemical species. The measurements made in vacuum will then provide signatures that can be used later to identify those species when water is present, in other words, in the reactor as it normally functions. The work addresses an important societal problem, the development of alternative sources of energy that do not rely on carbon-based fuels. Training the next generation of scientists is an integral part of this project. It includes budding researchers as young as grades five through nine through a Saturday morning science program.In this project, the investigators are studying the electronic and geometric structures of selected ruthenium- and copper-based catalysts for water oxidation, as well as certain reaction intermediates that arise in the catalytic conversion process. Ions of catalyst and reaction intermediates are transferred into the gas phase by electrospray ionization. The ions are then cooled in an ion trap, mass selected, and irradiated by pulsed light, which is tunable throughout the mid-IR, visible and near-UV spectrum. Photon absorption is monitored by photofragmentation of the target ions, allowing the measurement of their vibrational and electronic spectra. Cooling the ions to low temperatures is crucial to obtain the necessary spectroscopic detail. Vibrational spectra will result in structural information about the ions under study, which is particularly important for reaction intermediates. Measuring the electronic spectra of catalysts and reaction intermediates will aid clarification of speciation in reactive solutions. In addition, the excited state vibrational structure is assisting the investigators in computational modeling studies of the excited state dynamics and reactivity.