Understanding the High Activity of Fe-N-C Electrocatalysts in Oxygen Reduction: Fe/Fe3C Nanoparticles Boost the Activity of Fe-Nx
Understanding the High Activity of Fe-N-C Electrocatalysts in Oxygen Reduction: Fe/Fe3C Nanoparticles Boost the Activity of Fe-Nx
复制标题
了解 Fe-N-C 电催化剂在氧还原中的高活性：Fe/Fe3C 纳米粒子增强 Fe-N-x 的活性
DOI：
10.1021/jacs.6b00757
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发表时间：
2016-03-16
影响因子：
15
通讯作者：
Wan, Li-Jun
中科院分区：
文献类型：
--
作者：
Jiang, Wen-Jie;Gu, Lin;Wan, Li-Jun
了解Fe-N-C电催化剂在氧还原反应（ORR）中高活性的来源是开发高效、可持续的燃料非贵金属催化剂的关键，但仍然具有挑战性。电池和金属空气电池。在此，我们开发了一种含有Fe- n -x配位位点和Fe/Fe3C纳米晶体的新型高活性Fe- n - c ORR催化剂（Fe@C-FeNC），并通过深入研究催化剂的组成和结构及其与电化学性能的关系揭示了其活性的来源。详细分析结果明确了最佳催化剂中Fe/Fe3C纳米晶与Fe- n -x的共存。一系列设计的实验表明：(1)n掺杂碳衬底、Fe/Fe3C纳米晶体或Fe- n -x本身没有提供高活性；(2) Fe/Fe3C纳米晶和Fe- n -x催化剂均表现出较高的活性；(3) Fe-N-x含量越高，活性越高；(4) Fe/Fe3C纳米晶的去除严重降低了活性；(5) Fe-N-x的阻断使活性降低，阻断的Fe-N-x恢复后活性恢复。这些事实支持Fe@C-FeNC电催化剂的高ORR活性应归因于Fe/Fe3C纳米晶体提高了Fe- n -x的活性。高含量的Fe-N-x和足够的金属铁纳米颗粒的共存是高ORR活性的必要条件。DFT计算证实了这一结论，表明金属铁与Fe-N-4配位结构的相互作用有利于氧分子的吸附。这些新发现为合理设计和自下而上合成低成本高活性ORR电催化剂开辟了道路。
Understanding the origin of high activity of Fe-N-C electrocatalysts in oxygen reduction reaction (ORR) is critical but still challenging for developing efficient sustainable nonprecious metal catalysts in fuel. cells and metal air batteries. Herein, we developed a new highly active Fe-N-C ORR catalyst containing Fe-N-x coordination sites and Fe/Fe3C nanocrystals (Fe@C-FeNC), and revealed the origin of its activity by intensively investigating the composition and the structure of the catalyst and their correlations with the electrochemical performance. The detailed analyses unambiguously confirmed the coexistence of Fe/Fe3C nanocrystals and Fe-N-x in the best catalyst. A series of designed experiments disclosed that (1) N-doped carbon substrate, Fe/Fe3C nanocrystals or Fe-N-x themselves did not deliver the high activity; (2) the catalysts with both Fe/Fe3C nanocrystals and Fe-N-x exhibited the high activity; (3) the higher content of Fe-N-x gave the higher activity; (4) the removal of Fe/Fe3C nanocrystals severely degraded the activity; (5) the blocking of Fe-N-x downgraded the activity and the recovery of the blocked Fe-N-x recovered the activity. These facts supported that the high ORR activity of the Fe@C-FeNC electrocatalysts should be ascribed to that Fe/Fe3C nanocrystals boost the activity of Fe-N-x. The coexistence of high content of Fe-N-x and sufficient metallic iron nanoparticles is essential for the high ORR activity. DFT calculation corroborated this conclusion by indicating that the interaction between metallic iron and Fe-N-4 coordination structure favored the adsorption of oxygen molecule. These new findings open an avenue for the rational design and bottom-up synthesis of low-cost highly active ORR electrocatalysts.