Nitrogen-doped graphene (N-G) as a promising candidate of the oxygen reduction reaction (ORR) catalysts. However, the contributions of pyridinic N, pyrrolic N and graphitic N in N-G for the ORR catalytic activity are controversial. In this work, the N-G was synthesized by a facile annealing treatment. Graphene oxide (GO) was used as a support which has many oxygen species, and cheap urea was used as N precursors. The contents of pyridinic N, pyrrolic N and graphitic N in N-G were transformed by annealing with different temperatures. It is found that the total N content in N-G is not the critical factor to determine ORR activity. After the annealing treatment, the graphitic N content in the N-G samples increases from 1.13 at% (N-G-800) to 1.44 at% (N-G-1000). Specially, N-G-1000 possesses the highest proportion of graphitic N (41.54 %) among all the N-G samples. The increase annealing temperature can enhance the content of graphitic N in N-G, causing an improved catalytic ORR activity, which confirms that graphitic N is the active component. Moreover, the enriched graphitic N in N-G-1000 catalyst shows a half-wave potential (<i>E</i><sub>1/2</sub>) of 0.862 V, 29 mV higher than commercial Pt/C catalyst (0.833 V), which is one of the best ORR metal-free catalysts. The original catalytic current of N-G only a slight attenuation (retained 91.8 %) after continuous reaction for 10,000 s. This work may shed light on the further exploration of the N-doped graphene as an excellent ORR catalyst.

Enriched graphitic N in nitrogen-doped graphene as a superior metal-free electrocatalyst for oxygen reduction reaction

2019 Spring National Meeting

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