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Single Cobalt Sites Dispersed in Hierarchically Porous Nanofiber Networks for Durable and High‐Power PGM‐Free Cathodes in Fuel Cells
Advanced Materials ( IF 27.4 ) Pub Date : 2020-10-15 , DOI: 10.1002/adma.202003577 Yanghua He 1 , Hui Guo 2 , Sooyeon Hwang 3 , Xiaoxuan Yang 1 , Zizhou He 2 , Jonathan Braaten 4 , Stavros Karakalos 5 , Weitao Shan 6 , Maoyu Wang 7 , Hua Zhou 8 , Zhenxing Feng 7 , Karren L. More 9 , Guofeng Wang 6 , Dong Su 3 , David A. Cullen 9 , Ling Fei 2 , Shawn Litster 4 , Gang Wu 1
Advanced Materials ( IF 27.4 ) Pub Date : 2020-10-15 , DOI: 10.1002/adma.202003577 Yanghua He 1 , Hui Guo 2 , Sooyeon Hwang 3 , Xiaoxuan Yang 1 , Zizhou He 2 , Jonathan Braaten 4 , Stavros Karakalos 5 , Weitao Shan 6 , Maoyu Wang 7 , Hua Zhou 8 , Zhenxing Feng 7 , Karren L. More 9 , Guofeng Wang 6 , Dong Su 3 , David A. Cullen 9 , Ling Fei 2 , Shawn Litster 4 , Gang Wu 1
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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 CoN4 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 H2/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.
中文翻译：
单个钴位点分散在分层多孔纳米纤维网络中，以形成燃料电池中耐用且高功率的无PGM阴极
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（MC）催化剂的催化活性和耐久性的提高仍然是一个巨大的挑战。在这里，报道了一种通过将钴掺杂的沸石咪唑酸酯骨架电纺到选定的聚丙烯腈和聚（乙烯基吡咯烷酮）聚合物中而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层结构通过暴露更易接近的活性位点，提供便捷的电子传导性并促进反应物的质量传输，在提高电极性能方面起着至关重要的作用。增强的固有活性归因于围绕CoN 4的额外石墨N掺杂剂部分。催化剂中高度石墨化的碳基质有利于增强碳的耐腐蚀性，从而提高催化剂的稳定性。独特的纳米级X射线计算机断层扫描技术可验证催化剂中整个纤维碳网络中分布均匀的离聚物覆盖率。膜电极组件在实际的H 2 /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中显示出显着增强的耐久性。单个Co位点的固有活性和稳定性以及独特的催化剂体系结构的结合，为设计高效，不含PGM的电极提供了新的见解，并提高了性能和耐用性。
更新日期：2020-11-17
中文翻译：
单个钴位点分散在分层多孔纳米纤维网络中，以形成燃料电池中耐用且高功率的无PGM阴极
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（MC）催化剂的催化活性和耐久性的提高仍然是一个巨大的挑战。在这里，报道了一种通过将钴掺杂的沸石咪唑酸酯骨架电纺到选定的聚丙烯腈和聚（乙烯基吡咯烷酮）聚合物中而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层结构通过暴露更易接近的活性位点，提供便捷的电子传导性并促进反应物的质量传输，在提高电极性能方面起着至关重要的作用。增强的固有活性归因于围绕CoN 4的额外石墨N掺杂剂部分。催化剂中高度石墨化的碳基质有利于增强碳的耐腐蚀性，从而提高催化剂的稳定性。独特的纳米级X射线计算机断层扫描技术可验证催化剂中整个纤维碳网络中分布均匀的离聚物覆盖率。膜电极组件在实际的H 2 /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中显示出显着增强的耐久性。单个Co位点的固有活性和稳定性以及独特的催化剂体系结构的结合，为设计高效，不含PGM的电极提供了新的见解，并提高了性能和耐用性。
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