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Single Cobalt Sites Dispersed in Hierarchically Porous Nanofiber Networks for Durable and High‐Power PGM‐Free Cathodes in Fuel Cells
Author(s) -
He Yanghua,
Guo Hui,
Hwang Sooyeon,
Yang Xiaoxuan,
He Zizhou,
Braaten Jonathan,
Karakalos Stavros,
Shan Weitao,
Wang Maoyu,
Zhou Hua,
Feng Zhenxing,
More Karren L.,
Wang Guofeng,
Su Dong,
Cullen David A.,
Fei Ling,
Litster Shawn,
Wu Gang
Publication year - 2020
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.202003577
Subject(s) - materials science , electrospinning , catalysis , cobalt , nanofiber , chemical engineering , polyacrylonitrile , carbon nanofiber , cathode , proton exchange membrane fuel cell , carbon fibers , nanotechnology , polymer , composite material , carbon nanotube , organic chemistry , chemistry , composite number , engineering , metallurgy
Abstract Increasing catalytic activity and durability of atomically dispersed metal–nitrogen–carbon (M–N–C) catalysts for the oxygen reduction reaction (ORR) cathode in proton‐exchange‐membrane fuel cells remains a grand challenge. Here, a high‐power and durable Co–N–C nanofiber catalyst synthesized through electrospinning cobalt‐doped zeolitic imidazolate frameworks into selected polyacrylonitrile and poly(vinylpyrrolidone) polymers is reported. The distinct porous fibrous morphology and hierarchical structures play a vital role in boosting electrode performance by exposing more accessible active sites, providing facile electron conductivity, and facilitating the mass transport of reactant. The enhanced intrinsic activity is attributed to the extra graphitic N dopants surrounding the CoN 4 moieties. The highly graphitized carbon matrix in the catalyst is beneficial for enhancing the carbon corrosion resistance, thereby promoting catalyst stability. The unique nanoscale X‐ray computed tomography verifies the well‐distributed ionomer coverage throughout the fibrous carbon network in the catalyst. The membrane electrode assembly achieves a power density of 0.40 W cm −2 in a practical H 2 /air cell (1.0 bar) and demonstrates significantly enhanced durability under accelerated stability tests. The combination of the intrinsic activity and stability of single Co sites, along with unique catalyst architecture, provide new insight into designing efficient PGM‐free electrodes with improved performance and durability.