Multiscale structural engineering of atomically dispersed FeN4 electrocatalyst for proton exchange membrane fuel cells

Atomically dispersed iron-nitrogen-carbon (Fe-N-C) catalysts have emerged as the most promising alternative to the expensive Pt-based catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs), however suffer from low site density of active Fe-N-4 moiety and limited mass transport during the catalytic reaction. To address these challenges, we report a three-dimensional (3D) metal-organic frameworks (MOF)-derived Fe-N-C single-atom catalyst. In this well-designed Fe-N-C catalyst, the micro-scale interconnected skeleton, the nano-scale ordered pores and the atomic-scale abundant carbon edge defects inside the skeleton significantly enhance the site density of active Fe-N-4 moiety, thus improving the Fe utilization in the final catalyst. Moreover, the combination of the above mentioned micro- and nano-scale structures greatly facilitates the mass transport in the 3D Fe-N-C catalyst. Therefore, the multiscale engineered Fe-N-C single-atom catalyst achieves excellent ORR performance under acidic condition and affords a significantly enhanced current density and power density in PEMFC. Our findings may open new opportunities for the rational design of Fe-N-C catalysts through multiscale structural engineering. (C) 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.