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Boosting ORR Catalytic Activity by Integrating Pyridine‐N Dopants, a High Degree of Graphitization, and Hierarchical Pores into a MOF‐Derived N‐Doped Carbon in a Tandem Synthesis
Author(s) -
Liu Dandan,
Li Liangjun,
Xu Huanfei,
Dai Pengcheng,
Wang Ying,
Gu Xin,
Yan Liting,
Zhao Guoming,
Zhao Xuebo
Publication year - 2018
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201800245
Subject(s) - carbonization , catalysis , materials science , tafel equation , carbon fibers , pyrolysis , chemical engineering , metal organic framework , reversible hydrogen electrode , tandem , metal , inorganic chemistry , nanotechnology , chemistry , electrode , electrochemistry , organic chemistry , composite number , composite material , working electrode , scanning electron microscope , adsorption , engineering , metallurgy
N‐doped carbon materials represent promising metal‐free electrocatalysts for the oxygen reduction reaction (ORR), the cathode reaction in fuel cells, metal–air batteries, and so on. A challenge for optimizing the ORR catalytic activities of these electrocatalysts is to tune their local structures and chemical compositions in a rational and controlled way that can achieve the synergistic function of each factor. Herein, we report a tandem synthetic strategy that integrates multiple contributing factors into an N‐doped carbon. With an N‐containing MOF (ZIF‐8) as the precursor, carbonization at higher temperatures leads to a higher degree of graphitization. Subsequent NH 3 etching of this highly graphitic carbon enabled the introduction of a higher content of pyridine‐N sites and higher porosity. By optimizing these three factors, the resultant carbon materials displayed ORR activity that was far superior to that of carbon derived from a one‐step pyrolysis. The onset potential of 0.955 V versus a reversible hydrogen electrode (RHE) and the half‐wave potential of 0.835 V versus RHE are among the top ranks of metal‐free ORR catalysts and are comparable to commercial Pt/C (20 wt %) catalysts. Kinetic studies revealed lower H 2 O 2 yields, higher electron‐transfer numbers, and lower Tafel slopes for these carbon materials compared with that derived from a one‐step carbonization. These findings verify the effectiveness of this tandem synthetic strategy to enhance the ORR activity of N‐doped carbon materials.