Nano-Micro Letters

Facile Synthesis of N-doped Graphene-like Carbon Nanoflakes as Efficient and Stable Electrocatalysts for the Oxygen Reduction Reaction

Daguo Gu1, Yao Zhou2, Ruguang Ma2, *, Fangfang Wang2, Qian Liu2, 3, *, Jiacheng Wang2, 3, *

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Nano-Micro Lett. (2018) 10: 29

First Online: 04 December 2017 (Article)


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Fig. 6 Electrochemical oxygen reduction measurements in 0.1 M KOH solution. a Comparison of LSV curves for PC, NC-1, NC-3, NC-6, and commercial Pt/C catalyst at a scan rate of 10 mV s–1 and 1600 rpm in O2-saturated solution. b Dependence of half-wave potential (Ehalf) and current density on the mass ratio of dicyanamide (DCA) to citric acid. c CV curves of NC-6 in O2- or N2-saturated solution. d LSV curves of NC-6 and Pt/C at different rotation speeds (varying from 400 to 2025 rpm). e K-L plots of the samples based on the LSV curves at different rotation speeds and 0.4 V (vs. RHE). f Electron transfer number (n) calculated from the K-L plots of the various samples in the potential range of 0.2–0.5 V (vs. RHE)

A series of N-doped carbon materials (NCs) were synthesized by using biomass citric acid and dicyandiamide as renewable raw materials via a facile one-step pyrolysis method. The characterization of microstructural features shows that the NCs samples are composed of few-layered graphene-like nanoflakes with controlled in situ N-doping, which is attributed to the confined pyrolysis of citric acid within the interlayers of the dicyandiamide-derived g-C3N4 with high nitrogen contents. Evidently, the pore volumes of the NCs increased with the increasing content of dicyandiamide in the precursor. Among these samples, the NCs nanoflakes prepared with the citric acid/dicyandiamide mass ratio of 1:6, NC-6, show the highest N content of ~6.2 at%, in which pyridinic and graphitic-N groups are predominant. Compared to the commercial Pt/C catalyst, the as-prepared NC-6 exhibits a small negative shift of ~66 mV at the half-wave potential, demonstrating excellent electrocatalytic activity in the oxygen reduction reaction. Moreover, NC-6 also shows better long-term stability and resistance to methanol crossover compared to Pt/C. The efficient and stable performance are attributed to the graphene-like microstructure and high content of pyridinic and graphitic doped nitrogen in the sample, which creates more active sites as well as facilitating charge transfer due to the close four-electron reaction pathway. The superior electrocatalytic activity coupled with the facile synthetic method presents a new pathway to cost-effective electrocatalysts for practical fuel cells or metal-air batteries.



Nitrogen doping; Graphene-like; Carbon nanoflakes; Electrocatalyst; Oxygen reduction reaction

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