Hydrogen fuel cells are among the most promising next-generation power sources for future automotive transportation. Developing efficient, durable, and low-cost electrocatalysts to accelerate the sluggish oxygen reduction reaction (ORR) is urgently needed to advance fuel cell technologies.Now, in a new paper appearing in the Journal of the American Chemical Society, a team of researchers from Cornell and the University of Wisconsin report new catalysts which exhibit superior ORR activity and robust stability. The team has characterized metal–organic framework-derived nonprecious dual metal single-atom catalysts (SACs), consisting of Co–N4 and Zn–N4 local structures. Their remarkable performance was validated under realistic fuel cell working conditions, achieving a record-high peak power density of ∼1 W cm–2 among the reported SACs for alkaline fuel cells. Operando X-ray absorption spectroscopy studies at the PIPOXS beamline at CHEXS revealed that the Co atom in the Co–N4 structure is the main catalytically active center. This work provides a comprehensive mechanistic understanding of the active sites in the Zn/Co–N–C catalysts and will pave the way for the future design and advancement of high-performance single-site electrocatalysts for fuel cells and other energy applications.
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Image: Isolated Zinc and Cobalt atoms on a metal-organic-framework scaffold occupy local environments which are coordinated by 4 Nitrogen atoms. Using x-ray spectroscopy inside operating hydrogen fuel cells, the Cornell/Wisconsin team (with then-PhD-student Weixuan Xu as first author) were able to directly observe that specifically the Co-N4 sites were responsible for highly efficient catalysis of the oxygen reduction reaction. As oxygen bonds to a Co-N4 site, the Co XANES edge shifts to higher energy, providing a clear fingerprint for the reaction mechanism.