物理化学学报 >> 2021, Vol. 37 >> Issue (3): 1911011.doi: 10.3866/PKU.WHXB201911011

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基于血红素衍生的中空非贵金属催化剂氧还原反应电催化活性

李琳1, 沈水云1, 魏光华2, 章俊良1,3,*()   

  1. 1 上海交通大学机械与动力工程学院燃料电池研究所，上海 200240
    2 上海交通大学巴黎高科学院，上海 200240
    3 上海交通大学动力机械与工程教育部重点实验室，上海 200240
  • 收稿日期:2019-11-06 录用日期:2019-11-25 发布日期:2019-11-29
  • 通讯作者: 章俊良 E-mail:junliang.zhang@sjtu.edu.cn
  • 基金资助:
    国家自然科学基金(21533005);国家重点研发计划(2016YFB0101200)

Electrocatalytic Activity of Hemin-Derived Hollow Non-Precious Metal Catalyst for Oxygen Reduction Reaction

Lin Li1, Shuiyun Shen1, Guanghua Wei2, Junliang Zhang1,3,*()   

  1. 1 Institute of Fuel Cells, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
    2 SJTU-Paris Tech Elite Institute of Technology, Shanghai Jiao Tong University, Shanghai 200240, China
    3 MOE Key Laboratory of Power & Machinery Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
  • Received:2019-11-06 Accepted:2019-11-25 Published:2019-11-29
  • Contact: Junliang Zhang E-mail:junliang.zhang@sjtu.edu.cn
  • About author:Junliang Zhang, Email: junliang.zhang@sjtu.edu.cn; Tel.: +86-21-34207439
  • Supported by:
    the National Natural Science Foundation of China(21533005);the National Key Research and Development Program of China(2016YFB0101200)

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摘要：

血红素作为一种天然金属大环化合物常被用于制备非贵金属电催化剂用于燃料电池阴极的氧还原反应，但是其电催化活性仍有待提升。本文以氯化钠作为模板设计合成了一种中空的铁基非贵金属电催化剂Hemin-HD (Hemin hollow derivative)，在碱性介质中该催化剂可以高效地催化氧还原反应。结合透射电镜、X射线衍射、比表面积分析和X射线光电子能谱等物理化学表征可知，与无模板制备的电催化剂Hemin-D (Hemin derivative)相比，Hemin-HD电催化剂比表面积提升了6.5倍，孔容积增加了3.8倍。这主要是由于该电催化剂中空结构的设计使得催化活性位可以同时分散在内表面和外表面，比表面积的增加加强了活性位点的暴露，提高了活性位点密度。此外，Hemin-HD电催化剂中的孔道结构可以有效地改善氧气传质速率，加强活性位点与反应物之间的接触，从而有效提高催化剂的氧还原活性。

关键词: 氧还原反应, 非贵金属催化剂, 血红素, 氯化钠模板, 中空

Abstract:

In recent years, increasing efforts have been undertaken to develop non-precious metal (NPM) catalysts with both high activity and stability toward the oxygen reduction reaction (ORR), since they are much less expensive than commercially available Pt-based electrocatalysts. Transition metal macrocyclic compounds contain transition metal, nitrogen, and carbon species, hence becoming promising precursors for the synthesis of NPM catalysts. Hemin, a natural transition-metal-based macrocyclic compound, is widely applied to the synthesis of NPM electrocatalysts. However, the ORR activity of hemin-derived electrocatalysts must be improved considerably as compared with that of state-of-the-art NPM electrocatalysts. Morphology control is an efficient method to increase the exposure of active sites, thus enhancing the ORR activity. Here, we fabricated a hollow NPM electrocatalyst (hemin hollow derivative, Hemin-HD) using hemin as the precursor and NaCl as the template. First, hemin and NaCl were dispersed and mixed in solution. With an increase in the temperature, the solution was vapored and NaCl began to crystallize. Hemin wrapped the outer surface of NaCl because of the ionic interaction between these two compounds. The as-obtained powders were collected and carbonized at high temperature under a nitrogen atmosphere. Then, the NaCl template was removed by washing, and the hollow material Hemin-HD was obtained. Physicochemical characterization by transmission electron microscopy (TEM), X-ray diffraction (XRD), surface area measurements and X-ray photoelectron spectroscopy (XPS) confirmed that the surface area and pore volume of the as-obtained Hemin-HD electrocatalyst increased by a factor of 6.5 and 3.8, respectively, relative to those of the Hemin-D (hemin derivative) sample without the NaCl template. Owing to the hollow structure and increased surface area, the Fe and N content on the Hemin-HD surface were higher than those on the Hemin-D surface. Consequently, Hemin-HD showed better ORR activity in alkali solution than Hemin-D did, this was confirmed by the fact that the half-wave potential of Hemin-HD was greater than that of Hemin-D by 20 mV, and faster kinetics were observed for the former, as calculated by the Tafel slope. The performance of Hemin-HD was comparable to that of commercial Pt/C catalysts for the ORR in alkali solution. It is believed that the hollow structure allows the dispersion of active sites on both the inner and outer surfaces, thus facilitating the exposure of a great number of active sites. Besides, the pore structure of the electrocatalyst is expected to boost mass transfer and improve the contact between the active sites and reactants, thus enhancing the ORR activity.

Key words: Oxygen reduction reaction, Non-precious metal electrocatalyst, Hemin, NaCl template, Hollow