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
Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, NY, 14260, USA.
Department of Chemical Engineering, University of Louisiana at Lafayette, Lafayette, LA, 70504, USA.
Adv Mater. 2020 Nov;32(46):e2003577. doi: 10.1002/adma.202003577. Epub 2020 Oct 15.
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 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 in a practical H /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.
提高质子交换膜燃料电池中用于氧还原反应（ORR）阴极的原子分散金属 - 氮 - 碳（M - N - C）催化剂的催化活性和耐久性仍然是一个巨大的挑战。在此，报道了一种通过将钴掺杂的沸石咪唑框架电纺到选定的聚丙烯腈和聚乙烯吡咯烷酮聚合物中合成的高功率且耐用的Co - N - C纳米纤维催化剂。独特的多孔纤维形态和分级结构通过暴露更多可及的活性位点、提供便捷的电子传导性以及促进反应物的质量传输，在提高电极性能方面发挥着至关重要的作用。增强的本征活性归因于围绕CoN部分的额外石墨氮掺杂剂。催化剂中高度石墨化的碳基质有利于提高碳的耐腐蚀性，从而促进催化剂的稳定性。独特的纳米级X射线计算机断层扫描验证了整个催化剂纤维状碳网络中离聚物覆盖的良好分布。膜电极组件在实际的H₂/空气电池（1.0 bar）中实现了0.40 W cm⁻²的功率密度，并在加速稳定性测试下表现出显著增强的耐久性。单Co位点的本征活性和稳定性与独特的催化剂结构相结合，为设计具有改进性能和耐久性的高效无铂电极提供了新的见解。
