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

该项目将开发和应用新的方法，以了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方面具有优势。DMFC特别有吸引力，因为它可以随时获得甲醇，而且有可能从可再生资源中生产甲醇。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，以便提出更有效的催化剂材料和结构。开发的方法将推动直接甲醇燃料电池技术走向更广泛的商业应用，从而实现更清洁和更高效的能源生产。该项目将通过首次演示液相电化学稳态同位素瞬变动力学分析(SSITKA)，实现一种新的活性催化中心操作数计算方法。该方法的开发将利用作为探针系统的电化学甲醇氧化反应(MOR)在碳负载的铂(PT)和铂-Ru(PtRu)上进行。在这些材料上，MOR涉及几个知名的中间体，它产生的产品可以通过SSITKA和辅助技术进行表征，这些辅助技术可以证实SSITKA数据。将使用补充分析，包括原位红外光谱和许多X射线和电子材料表征技术，以便对反应机理进行全面检查。将沿着两个主题中的几条调查路线产生新的理解。主题I将侧重于实验动力学，并将SSITKA数据(从一系列实验条件、催化剂颗粒大小和催化剂组成获得)与将电流-电压特性与可能的基本步骤相关联的微观动力学模型联系起来。Theme II将利用广泛的非原位和原位表征方法，根据催化剂组成和合成方法来识别和控制活性中心。综上所述，这两个主题应该会对控制催化电化学甲醇氧化的活性和选择性的因素产生前所未有的洞察力，同时也为SSITKA技术的开发和完善提供了一个平台。从技术的角度来看，SSITKA技术对动力学、详细的反应机理和催化剂结构-功能关系的基本理解将可以转化为广泛的电化学反应。与其他技术相结合，它将提供关于活性材料和表面结构的见解，从而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开发的几项教育和推广活动。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。

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.