物理化学学报 >> 2019, Vol. 35 >> Issue (7): 740-748.doi: 10.3866/PKU.WHXB201809003

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基于金属有机框架衍生的Fe-N-C纳米复合材料作为高效的氧还原催化剂

王倩倩,刘大军,何兴权*()   

  • 收稿日期:2018-09-03 发布日期:2018-12-21
  • 通讯作者: 何兴权 E-mail:hexingquan@hotmail.com
  • 基金资助:
    the Natural Science Foundation of Jilin Province, China(20160101298 JC); 

Metal-Organic Framework-Derived Fe-N-C Nanohybrids as Highly-Efficient Oxygen Reduction Catalysts

Qianqian WANG,Dajun LIU,Xingquan HE*()   

  • Received:2018-09-03 Published:2018-12-21
  • Contact: Xingquan HE E-mail:hexingquan@hotmail.com
  • Supported by:
    the Natural Science Foundation of Jilin Province, China(20160101298 JC); 

摘要:

开发用于氧还原反应(ORR)的低成本和高性能的非贵金属催化剂(NPMC)对于燃料电池的商业化至关重要。在这里,我们介绍了一种简单合成的由Fe3C纳米粒子包裹在介孔N掺杂碳(Fe-NC)中的NPMC材料,包括MIL-100(Fe)与葡萄糖和尿素的物理混合,以及随后在惰性气体下的热解。由此获得的Fe-N-C-900 (在900 ℃下制备的材料)表现出优异的电催化活性,高耐久性和对ORR卓越的甲醇耐受性,其催化性能与商业Pt/C在碱性介质中的催化性能相当。Fe-N-C-900在ORR中表现出优异的催化活性和稳定性,这是由于其较大的BET比表面积,较大的孔体积,氮掺杂剂,活性Fe3C纳米粒子以及其中活性官能团之间的协同效应。

关键词: 电催化剂, 氧还原反应, 金属有机框架, Fe3C纳米粒子, 协同效应

Abstract:

Environmentally friendly and renewable energy technologies, such as fuel cells and metal-air batteries, hold great promise for solving current energy and environmental challenges. The oxygen reduction reaction (ORR) plays a pivotal role in this top-drawer question. However, the sluggish kinetics of the ORR and prohibitive costs limit the global scalability of such devices. Traditionally, platinum-based electrocatalysts exhibit the best performance for ORRs in both acid and alkaline electrolytes. However, to significantly reduce the cost and realize sustainable development, utilization of Pt must be replaced or significantly reduced in the ORR cathode for fuel cell applications. Therefore, developing earth-abundant and high-performance non-precious metal catalysts (NPMCs) for ORR is of critical importance for the commercialization of fuel cells. In comparison to traditional catalysts, metal-organic frameworks (MOFs) are ideal precursors that integrate metal, nitrogen, and carbon functionalities together into one ordered 3D crystal structure. MOFs, assembled by secondary building of units comprised of metals and organic linkers with strong bonding, have received significant research attention because they possess permanent porosity, a three-dimensional (3D) structure, and can be prepared using a diversity of metals and organic linkers. High surface area, and microporous carbon materials can be easily obtained by carbonization of MOFs at high temperatures. In particular, MOF-derived carbon nanocomposites, which were prepared from transition metals, and have the form M-N-C (M = Fe or Co), have demonstrated remarkably improved catalytic activity and stability. Herein, we report an NPMC material consisting of Fe3C nanoparticles encapsulated in mesoporous N-doped carbon (Fe-N-C), synthesized by a simple strategy involving physical mixing of MIL-100(Fe) with glucose and urea, and subsequent pyrolysis under inert atmosphere. The strong interaction between metal atoms and nitrogen atoms is beneficial in generating more active sites, and sites with a higher intrinsic catalytic activity, via carbonization. The as-obtained catalysts exhibit remarkable ORR activity in alkaline media, with the best catalyst (Fe-N-C-900, which is synthesized at 900 ℃) featuring a more positive onset potential (0.96 V vs the reversible hydrogen electrode (RHE)), a more positive half-wave potential (0.83 V vs RHE), a much higher diffusion limiting current density (6.28 mA·cm-2) and a larger electron-transfer number (n), even at low overpotentials, compared with other contrast materials. Fe-N-C-900's excellent catalytic activity and stability in ORR are due to its large BET surface area, its large total pore volume, its nitrogen dopants, its active Fe3C nanoparticles and the cooperative effects among its reactive functionalities.

Key words: Electrocatalyst, Oxygen reduction reaction, Metal-organic frameworks, Fe3C nanoparticles, Synergistic effect

MSC2000: 

  • O646