Collaborative Research: Engineering Atomically Dispersed Metal-Site Air Cathodes via Electrospinning at Multi-Scales for Low-Temperature Fuel Cells

氢质子交换膜燃料电池（pemfc）由于其高能量密度和高效率，对未来的汽车电气化至关重要，特别是在重型和远程运输应用中。然而，昂贵而稀缺的铂催化剂阻碍了pemfc的广泛应用，应该用地球上丰富的元素来取代。嵌入碳中的原子分散和氮配位过渡金属位点（如铁、钴和锰）已成为pemfc中有前途的低成本空气阴极。催化剂使用的一个技术障碍是其固有活性难以在实际氢燃料电池的膜电极组件中转移，因为稳定性不足，催化剂利用率低，碳腐蚀严重，质量传输差。该项目的成果将推动设计可持续和地球丰富的催化剂的知识，并将其整合到氢燃料电池和其他电化学能源技术的高性能电极中。这种廉价和清洁的能源技术直接有利于交通电气化和电网规模的可再生能源储存和转换，这对能源和环境的可持续性至关重要。该联合项目还为路易斯安那州南部和纽约州西部代表性不足的学生提供了与氢能源科学和技术相关的教育和推广活动的绝佳机会。该合作项目旨在通过静电纺丝方法将高活性的单金属位点催化剂结合到纤维电极中，为高效的空气阴极建立有利且坚固的三相界面。静电纺丝技术还可以构建有效的纳米纤维形态，并确保催化层中有足够的介孔和宏孔，以实现有效的质量/电荷传输和临界质子电导率，从而显著提高性能和耐用性。通过控制催化剂前驱体和电纺丝聚合物，可以调节原子分散活性金属位的配位环境和局部碳结构。将开发创新策略来构建具有平衡孔隙率和形态的纤维电极结构，以实现良好的质量/电荷传输，均匀的离聚体分散，最大限度地利用催化剂，并提高稳定性。从该项目中获得的基本知识和理解包括基于创新金属有机框架的催化剂前体的合理设计，以提高内在活性和位点密度，聚合物纤维的化学和结构与衍生碳纳米结构和形态之间的相关性，以及在三维空气阴极中衍生碳纳米纤维的孔结构和几何形状的精确控制。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。

Hydrogen proton-exchange membrane fuel cells (PEMFCs) are vital for future vehicle electrification, particularly in heavy-duty and long-range transportation applications, due to their high-energy density and high efficiency. However, the expensive and scarce platinum catalysts hinder the widespread applications of PEMFCs and should be replaced by earth-abundant elements. Atomically dispersed and nitrogen coordinated transition metal sites (e.g., iron, cobalt, and manganese) embedded in carbon have emerged as promising low-cost air cathodes in PEMFCs. One technical barrier concerning the catalyst’s use is that their intrinsic activity is difficult to transfer in the membrane electrode assemblies in actual hydrogen fuel cells because of insufficient stability, low catalyst utilization, severe carbon corrosion, and inferior mass transport. This project's outcomes will advance the knowledge of designing sustainable and earth-abundant catalysts and their integration into high-performance electrodes for hydrogen fuel cells and other electrochemical energy technologies. Such inexpensive and clean energy technologies directly benefit transportation electrification and grid-scale renewable energy storage and conversion, which are essential for energy and environmental sustainability. The joint project also provides excellent opportunities for education and outreach activities associated with hydrogen energy science and technologies for under-representative students in southern Louisiana and western New York. The collaborative project aims to incorporate highly active single metal site catalysts into fibrous electrodes via electrospinning approaches to establish favorable and robust three-phase interfaces for efficient air cathodes. The electrospinning technique could also construct effective nanofiber-based morphology and ensure sufficient meso- and macro-porosities in catalytic layers for efficient mass/charge transports and critical proton conductivity, leading to significant performance and durability improvements. The ligand coordination environments and local carbon structures of atomically dispersed active metal sites will be regulated through controlling catalyst precursors and electrospinning polymers. Innovative strategies will be developed to construct fibrous electrode architecture with balanced porosities and morphologies for favorable mass/charge transport, uniform ionomer dispersion, maximized catalyst utilization, and improved stability. The fundamental knowledge and understanding gained from this project include the rational design of catalyst precursors in boosting intrinsic activity and site density based on innovative metal-organic frameworks, the correlations between chemistry and structures of polymer fibers and the derived carbon nanostructure and morphologies, and the precise control of the pore structures and geometry of the derived carbon nanofibers within the three-dimensional air cathodes.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.