Scalable fabrication and active site identification of MOF shell-derived nitrogen-doped carbon hollow frameworks for oxygen reduction
Scalable fabrication and active site identification of MOF shell-derived nitrogen-doped carbon hollow frameworks for oxygen reduction
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DOI：
10.1016/j.jmst.2020.07.007
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发表时间：
2021-03-10
影响因子：
10.9
通讯作者：
Mai, Liqiang
中科院分区：
文献类型：
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作者：
Meng, Jiashen;Liu, Ziang;Mai, Liqiang
氮掺杂碳材料由于具有高活性、高比表面积、高电导率和低成本等优点，在燃料电池和金属-空气电池中具有广阔的应用前景。为了最大化其催化效率，非常需要具有丰富暴露活性位点的高效电催化剂的合理设计。此外，由于氮物种的复杂性，确定ORR的活性氮位点仍然具有挑战性。本文发展了一种简单易行的模板法来构建高浓度氮掺杂的碳中空骨架（NC），并在实验分析和理论计算的基础上揭示了不同氮物种对其ORR活性的影响。研究结果表明，ZIF-8分子筛在ZnO模板上的低压气相超组装、原位碳化和模板去除是其形成机理。与其他NC-700和NC-900样品相比，获得的NC-800显示出更好的ORR活性。结果表明，NC-800具有良好的上级ORR活性主要是由于其三氮组分含量的平衡。石墨态N和吡咯态N位是降低功函数的主要原因，而吡啶态N和吡咯态N位作为可能的活性位有利于提高态密度。(C)2021由Elsevier Ltd代表Journal of Materials Science & Technology编辑部出版。
Nitrogen-doped carbon materials as promising oxygen reduction reaction (ORR) electrocatalysts attract great interest in fuel cells and metal-air batteries because of their relatively high activity, high surface area, high conductivity and low cost. To maximize their catalytic efficiency, rational design of efficient electrocatalysts with rich exposed active sites is highly desired. Besides, due to the complexity of nitrogen species, the identification of active nitrogen sites for ORR remains challenging. Herein, we develop a facile and scalable template method to construct high-concentration nitrogen-doped carbon hollow frameworks (NC), and reveal the effect of different nitrogen species on their ORR activity on basis of experimental analysis and theoretical calculations. The formation mechanism is clearly revealed, including low-pressure vapor superassembly of thin zeolitic imidazolate framework (ZIF-8) shell on ZnO templates, in situ carbonization and template removal. The obtained NC-800 displays better ORR activity compared with other NC-700 and NC-900 samples. Our results indicate that the superior ORR activity of NC-800 is mainly attributed to its content balance of three nitrogen species. The graphitic N and pyrrolic N sites are responsible for lowering the working function, while the pyridinic N and pyrrolic N sites as possible active sites are beneficial for increasing the density of states. (C) 2021 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.