MOF-derived Co nanoparticles embedded in N,S-codoped carbon layer/MWCNTs for efficient oxygen reduction in alkaline media
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The hydrothermal reaction of cobalt salt in the presence of 4-pyridyl-tetrathiafulvalene-4-pyridyl (4-py-TTF-4-py) and terephthalic acid (PTA) has been employed for the preparation of a novel metal–organic framework (MOF), i.e., (4-py-TTF-4-py)2M2(PTA)4 (M = Co2+). The obtained MOF is then used as a starting material for the synthesis of Co nanoparticles embedded in N,S-codoped carbon layer and supported on multi-walled carbon nanotubes (Co@NSC/MWCNTs) through the high-temperature calcination. Specifically, the calcination leads to the formation of N,S-codoped carbon-coated Co nanoparticles with simultaneous growth on the MWCNTs due to decomposition of the MOF. When used as the electrocatalyst, the Co@NSC/MWCNTs are found to have a higher activity for the oxygen reduction reaction (ORR) and follow a four-electron pathway. The catalytic activity of the Co@NSC/MWCNTs is much higher than that of the pure MWCNTs and the MOFs/MWCNTs. Although the Co@NSC/MWCNTs still exhibit slightly higher overpotential for the ORR, it is indeed more kinetically facile than the commercial Pt/C catalyst, as demonstrated by its higher limiting current density and lower Tafel slope. Additionally, the Co@NSC/MWCNTs also show superior stability and better tolerance to methanol crossover and CO poisoning, compared with those of the commercial Pt/C catalyst. These results strongly suggest that the Co@NSC/MWCNTs could be used as one of the most promising ORR electrocatalysts for the ORR with great potential to replace the Pt/C. The work present here opens up a new route for the design of carbon-integrated ORR electrocatalysts with high performance from a great number of available and yet rapidly growing MOFs.
KeywordsMetal–organic framework N,S-codoped carbon Multi-walled carbon nanotube Oxygen reduction reaction Nonprecious metal electrocatalyst
This work is supported by the Chinese National Natural Science Foundation (Nos. U1532139 and 21476156), the Ningbo Natural Science Foundation (No. 2017A610059), Fundamental Research Funds for the Central Universities of SCUT (No.2018ZD25), the Guangdong Provincial Natural Science Foundation (No. 2017A030313092), and the Guangdong Innovative and Entepreneurial Research Team Program (No. 2014ZT05N200).
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