Mesoporous, nitrogen-doped, graphitized carbon nanosheets embedded with cobalt nanoparticles for efficient oxygen electroreduction
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Nitrogen-doped graphitized carbon nanosheets embedded with crystalline cobalt nanoparticles are facilely synthesized with the aid of melamine-containing hydrogen-bonded organic frameworks (HOF). Experimentally, HOF microrods with an in situ polymerized dopamine (DA) overlayer are coordinated with Co2+ cations and used as a precursor. After pyrolyzing the Co@DA-HOF precursor, irregular sheet-like carbons comprising a large number of Co nanoparticles as well as abundant mesopores are obtained (Co@MPC-T). The thermal decomposition of melamine-containing HOF microrods during high-temperature pyrolysis helps generate the abundant porous structures in the resulting catalyst samples. Thus, synthesized Co@MPC-T catalysts display an apparent ORR activity, and the one pyrolyzed at 800 °C is determined to show the highest ORR catalytic activity among the series, with a half-wave potential of + 0.796 V, a diffusion-limiting current density of 5.492 mA cm−2 at + 0.200 V and a kinetic current of 51.40 mA cm−2 that is even two times higher than the 20.10 mA cm−2 for commercial Pt/C catalyst. Moreover, benefiting from the protection of graphitized carbon overlayer, Co@MPC-800 shows a substantially higher operation stability as well as superior tolerance to fuel crossover, as compared with the commercial Pt/C catalyst. The remarkable ORR performance of Co@MPC-800 highlights the high potential of graphitized two-dimensional carbon composites with nonprecious transition metal nanoparticles in electrocatalysis.
This work was supported by the National Natural Science Foundation of China (NSFC 51402111 and 21528301), Guangdong Innovative and Entrepreneurial Research Team Program (2014ZT05N200) and the Fundamental Research Funds for the Central Universities (SCUT Grant No. 2018ZD21).
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The authors declare that they have no conflict of interest.
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