CAREER: Probing and Controlling Acidic Electrocatalytic Oxidation Mechanisms and Catalyst Degradation Processes

随着我们全球能源格局的演变，越来越多的可再生电力来自风能、太阳能和水力发电技术，电化学过程将成为燃料和化学品的主要来源。氢是许多燃料和化学品的关键成分，因此美国的氢需求预计将在未来30年增长2-5倍。质子交换膜(PEM)电解槽是一种很有前途的大规模可持续水制氢技术，但开发高效、稳定的酸性条件下水氧化催化剂一直是阻碍其推广应用的一个长期障碍。该项目将1)研究一类精确调整的催化剂材料，该材料旨在以最少的昂贵和战略贵金属的使用来承受PEM电解槽的严酷氧化和酸性条件，以及2)表征催化剂结构和反应机理之间的关键关系，如与反应速度和电能的有效利用有关。这项工作的科学成果将提高可再生能源生产燃料和化学品的可持续工艺的技术可行性。此外，这项研究将与新课程和课堂活动的合作开发和实施的可持续计划相结合，通过与芝加哥公立高中教师的合作，强调学生参与以提高对来自不同背景的学生的保留，并满足下一代科学标准。该项目重点关注酸性条件下的水氧化作为一种关键但相对简单的电化学氧化反应，用于基础研究钙钛矿型氧化物催化剂的反应机理、表面结构演变和失活过程，作为其电子和几何结构属性的函数。与IrO2和Ir/C基准催化剂相比，钙钛矿型氧化物结构为系统地调节催化剂的表面和本体性能提供了一个可调的平台，同时利用了较低的Ir负载量。原位光谱和动力学同位素研究将探索反应机理的趋势，并评估催化剂表面重组的程度与材料性质(氧化态、金属-氧键共价、金属-氧-金属键角等)的关系。以及反应条件。显微镜、电化学石英晶体微天平和交流阻抗谱将监测作为长期测试结果的形态、质量变化和电荷传输效应，以提供对各种失活过程的深入了解。这项工作还将建立固有的催化剂材料稳定性指标，以补充更普遍的性能稳定性指标，以指导高性能电催化系统的开发。这项工作产生的基本机械见解和结构理解将填补金属氧化物催化剂设计和系统控制的主要知识空白，这些催化剂驱动广泛的选择性电化学氧化反应。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。

As our global energy landscape evolves to incorporate a greater fraction of renewable electricity from sources such as wind, solar, and hydroelectric technologies, electrochemical processes will become a major source of fuels and chemicals. Hydrogen is a critical component of many fuels and chemicals, such that hydrogen demand in the US is projected to increase 2-5 times over the next 30 years. Proton exchange membrane (PEM) electrolyzers are a promising technology for large-scale, sustainable production of hydrogen from water, but development of efficient and stable catalysts for water oxidation in acidic conditions has been a longstanding roadblock for widespread implementation. The project will 1) investigate a class of precisely tuned catalyst materials that are designed to withstand the harsh oxidative and acidic conditions of PEM electrolyzers with minimal use of expensive and strategic precious metals, and 2) characterize critical relationships between catalyst structures and reaction mechanisms, as related to reaction rates and efficient utilization of electrical energy. The scientific outcomes of this work will lead to improved technological feasibility of sustainable processes for production of fuels and chemicals from renewable electricity sources. Furthermore, the research will be integrated with a sustainable plan for collaborative development and implementation of new curriculum and classroom activities that emphasize student engagement to improve retention of students from diverse backgrounds and fulfill Next Generation Science Standards, via work with Chicago Public High School teachers.This project focuses on water oxidation in acidic conditions as a critical, yet comparatively simple, electrochemical oxidation reaction for fundamental study of reaction mechanisms, surface structure evolution, and deactivation processes for perovskite oxide catalysts as a function of their electronic and geometric structure properties. Perovskite oxide structures provide a tunable platform for systematically modulating properties of catalysts both at the surface and in the bulk, while utilizing lower loadings of iridium compared to IrO2 and Ir/C benchmark catalysts. In situ spectroscopy and kinetic isotope studies will probe trends in reaction mechanisms and assess extent of catalyst surface reorganization with relation to material properties (oxidation states, metal-oxygen bond covalency, metal-oxygen-metal bond angle, etc.) and reaction conditions. Microscopy, electrochemical quartz crystal microbalance, and impedance spectroscopy will monitor morphology, mass changes, and charge transport effects as a result of long-term testing to provide insights to various deactivation processes. This work will also establish intrinsic catalyst material stability metrics to complement more ubiquitous performance stability metrics to guide development of high performance electrocatalytic systems. Fundamental mechanistic insights and structural understanding arising from this work will fill major knowledge gaps for design and systematic control of metal oxide catalysts that drive a wide range of selective electrochemical oxidation reactions.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.