CAREER: Understanding Bifunctionality in Organic Electro-oxidation Catalysis

风电场、光伏设备和水力发电等来源的可再生电能可用于进行广泛的化学反应，这些化学反应对燃料电池、废水处理、传感器和化学制造至关重要。目前，这些反应的能源主要来自化石燃料，但可再生电力提供了确保我们国家未来能源安全的机会，同时大幅减少了对环境的影响。该项目将开发和应用新的分析工具，以了解使电化学反应高效所需的分子水平过程。重点将放在了解如何利用电力和水中的氧气将甲醇直接转化为甲酸和甲醛等商品化学品。同样的工具也可以应用于甲醇燃料电池的发电设计。来自甲醇研究的见解将为将电化学催化应用于广泛的有机分子提供一个框架。这项研究将与教育和外展活动相结合，包括与一所地区高中合作的“能源学院”计划。有机电氧化反应对废水处理、传感、分布式化学合成和大量直接有机燃料电池的应用至关重要。其中许多技术可以建立在一个相互关联的单碳分子化学网络上，涉及甲醇、甲醛、甲酸和一氧化碳的氧化。在电氧化文献和其他催化领域中，“双功能”催化的作用--其中一个催化剂组分选择性地活化有机物，另一个选择性地活化水以形成活性氧物种--已经得到了广泛的推广。本项目旨在对双组分电氧化催化剂的工作机理(双功能或其他)进行分类和合理化，并展示控制有机小分子部分或全部氧化的设计原则。首席研究员最近开发的分析平台将用于在流动中快速整体电解过程中对定义良好的双金属纳米结构进行动力学测量。该系统还形成了第一个真正的液态电化学稳态同位素-瞬变动力学分析的基础，允许使用在线电化学质谱仪直接测量产品特定的活性中心覆盖范围(通过在其他稳定状态反应期间通过表面同位素交换观察到)。通过低能离子散射的顶原子层表面分析和其他辅助表征方法，包括材料的原位红外光谱和电子显微镜，将利用进一步的见解，以了解双功能氧化的机理，并利用这些知识设计新的催化材料。需要回答的关键问题涉及确定活性中心的性质(例如，碳-氧耦合步骤是否发生在界面上，而不是溢出现象)、它们的分布以及由此产生的相互作用(例如，改变一个功能组分如何无意中影响另一个功能组分)，最终目标是合理控制电催化剂的活性、选择性和稳定性。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Renewable electrical energy from sources such as wind farms, photovolataic devices, and hydroelectric power can be used to carry out a wide range of chemical reactions important for fuel cells, wastewater treatment, sensors, and chemical manufacturing. Currently, the energy for those reactions is derived primarily from fossil fuels, but renewable electricity offers opportunities to secure our nation's energy future while dramatically decreasing environmental impacts. The project will develop and apply new analytical tools to understand the molecular-level processes needed to make electrochemical reactions efficient. Focus will be placed on understanding ways to use electricity and the oxygen in water to directly convert methanol into commodity chemicals such as formic acid and formaldehyde. The same tools can be applied to the design of methanol fuel cells for energy generation. Insights from the methanol studies will provide a framework for applying electrochemical catalysis to a wide range of organic molecules. The research will be integrated with educational and outreach activities, including an "Energy Academy" program with a regional high-school. Organic electro-oxidation reactions are critical to applications in wastewater treatment, sensing, distributed-scale chemical synthesis, and a multitude of direct-organic fuel cells. Many of these technologies can be built around an interconnected network of single-carbon molecule chemistries involving oxidation of methanol, formaldehyde, formic acid and carbon monoxide. A role for "bifunctional" catalysis - in which one catalyst component selectively activates the organic and the other selectively activates water to form reactive oxygen species - has been widely promoted in the electro-oxidation literature, as well as other areas of catalysis. This project seeks to classify and rationalize the operative mechanisms (bifunctional or otherwise) of two-component electro-oxidation catalysts, and to demonstrate design principles for controlling partial or total oxidation of small organic molecules. An analytical platform, recently developed by the principal investigator, will be used to perform kinetic measurements on well-defined bimetallic nanostructures during rapid bulk electrolysis in flow. The system also forms the basis for the first true liquid electrochemical implementation of steady-state isotope-transient kinetic analysis, permitting direct measurement of product-specific active-site coverages (observed via surface isotope exchange during an otherwise-steady-state reaction) using online electrochemical mass spectrometry. Further insight will be leveraged from top-atomic layer surface analysis by low-energy ion scattering and other auxiliary characterization methods including in-situ infrared spectroscopy and electron microscopy of materials in order to understand the mechanistic pathways governing bifunctional oxidation, and use that knowledge to design new catalytic materials. Critical questions to be answered relate to the determination of the nature of the active sites (e.g. whether carbon-oxygen coupling steps happen at interfaces as opposed to spillover phenomena), their distribution, and their resulting interactions (e.g. how altering one functional component may inadvertently influence the other), with the ultimate goal to rationally control the activity, selectivity, and stability of the electrocatalysts.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.