EAGER: Identifying Active Sites in Electrocatalysis by Steady-State Isotope-Transient Technique

该项目将开发和应用新方法来理解适用于直接甲醇燃料电池（dmfc）催化剂设计的分子水平过程。使用液体燃料的燃料电池在能量密度、安全性以及燃料运输和储存的便利性方面具有优势。dmfc尤其具有吸引力，因为甲醇随时可用，而且有可能从可再生资源生产甲醇。然而，目前DMFC技术的能量转换效率较低，限制了其广泛应用。这项工作将提供对DMFC中发生的催化反应的详细了解，从而可以提出更有效的催化剂材料和结构。所开发的方法将推动直接甲醇燃料电池技术朝着更广泛的商业应用方向发展，从而实现更清洁、更高效的能源生产。该项目将通过液相电化学稳态同位素-瞬态动力学分析（SSITKA）的首次演示，为活性催化位点的operando计数提供一种新方法。该方法的开发将利用碳负载铂（Pt）和铂钌（PtRu）上的电化学甲醇氧化反应（MOR）作为探针系统。在这些材料上，MOR涉及几个众所周知的中间体，它产生的产品可以通过SSITKA和辅助技术进行表征，可以证实SSITKA的数据。补充分析，包括现场红外光谱和许多x射线和电子基材料表征技术，将用于告知反应机制的整体检查。新的理解将产生沿着几条线的调查捕获在两个主题。主题1将侧重于实验动力学，并将SSITKA数据-通过一系列实验条件，催化剂粒度和催化剂成分-与将电流-电压特性与可能的基本步骤联系起来的微动力学模型联系起来。主题二将利用广泛的非原位和原位表征方法来识别和控制活性位点作为催化剂组成和合成方法的功能。综上所述，这两个主题应该对控制催化电化学甲醇氧化活性和选择性的因素产生前所未有的见解，同时也为SSITKA技术的发展和改进提供了一个平台。从技术的角度来看，SSITKA技术在动力学、详细的反应机制和催化剂结构-功能关系方面的基本理解将被转化为广泛的电化学反应。结合其他技术，它将提供有关活性材料和表面结构的见解，这将指导设计性能更好的催化剂。该项目还将支持电化学和可再生能源领域的研究生和本科生教育，以及首席研究员已经在开发的一些教育和推广活动。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The project will develop and apply new methods to understand molecular-level processes applicable to the design of catalysts for direct methanol fuel cells (DMFCs). Fuel cells utilizing liquid fuels pose benefits in energy density, safety, and ease of fuel transport and storage. DMFCs, in particular, are attractive because of ready availability of methanol, and the potential for producing methanol from renewable resources. However, the low energy conversion efficiency of current DMFC technology has curtailed widespread use. This work will provide detailed understanding of the catalytic reactions that occur in a DMFC, such that more efficient catalyst materials and structures may be proposed. The methods developed should advance direct methanol fuel cell technology along the path toward broader commercial application, thereby enabling cleaner and more efficient energy production.The project will enable a new method for operando counting of active catalytic sites via the first demonstration of liquid-phase electrochemical steady-state isotope-transient kinetic analysis (SSITKA). The method development will utilize - as a probe system - the electrochemical methanol oxidation reaction (MOR) over carbon-supported platinum (Pt) and platinum-ruthenium (PtRu). On these materials, the MOR involves several well-known intermediates, and it yields products that are amenable to characterization by both SSITKA and auxiliary techniques that can corroborate SSITKA data. Complementary analyses, including in-situ infrared spectroscopy and numerous X-ray and electron-based materials characterization techniques, will be used to inform a holistic examination of the reaction mechanism. New understanding will be generated along several lines of inquiry as captured in two themes. Theme I will focus on experimental kinetics, and will link SSITKA data - obtained across a range of experimental conditions, catalyst particle sizes, and catalyst compositions - to microkinetic models that relate current-voltage characteristics to possible elementary steps. Theme II will utilize a broad range of ex-situ and in-situ characterization methods to identify and control active sites as a function of catalyst composition and synthesis methods. Taken together, the two themes should generate unprecedented insight regarding the factors that control activity and selectivity of catalytic electrochemical methanol oxidation, while also providing a platform for development and refinement of the SSITKA technique. From a technological point of view, the fundamental understanding enabled by the SSITKA technique with respect to kinetics, detailed reaction mechanisms, and catalyst structure-function relationships will be translatable to a broad range of electrochemical reactions. In combination with other techniques, it will provide insight regarding active materials and surface structures that will guide the design of better-performing catalysts. The project will also support graduate and undergraduate education in the area of electrochemistry and renewable energy, as well as several educational and outreach activities already under development by the principal investigator.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.