The synthesis of iron-nitrogen sites embedded in electrospun carbon nanofibers with an excellent oxygen reduction reaction activity in alkaline/acidic media
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摘要: 金属氮碳型催化剂，因其高活性、大比表面积和有效的气体扩散途径，在涉气电催化领域受到高度关注。本文采用静电纺丝法和退火处理制备了镶陷铁氮活性位点的碳纳米纤维，通过在聚丙烯腈前驱体中引入g-C3N4来增强纳米纤维中Fe在氮位点上的锚定，阻止热退火过程铁纳米颗粒的形成，从而提高碱性和酸性介质中的氧还原性能（明显优于不使用g-C3N4时所得的Fe3C/CNF对照样）。所制备的Fe/CNF催化剂，表现为4e路径电还原氧的催化活性；阴极催化锌空电池的性能良好：开路电压1.49 V，功率密度146 mW cm−2，比容量703 mAh g−1。本工作呈现了一种制备涉氧电池的金属-氮-碳纳米纤维催化剂的策略。Abstract: Metal-nitrogen carbon catalysts have received great attention in the field of gas-evolving electrocatalysis due to their high activity, large specific surface area and efficient gas diffusion paths. A solution of porphyrin iron, g-C3N4 and polyacrylonitrile in N,N-dimethylformamide was sonicated and electrospun into doped polyacrylonitrile nanofibers (NFs), and the NFs were then stabilized and carbonized at 900 °C to prepare Fe-N/CNF catalyst for oxygen reduction reaction (ORR). It was found that the addition of g-C3N4 to the electrospinning precursor led to the formation of abundant Fe-N species in Fe3+ and Fe2+ valence states, while Fe3C nanoparticles were formed without adding g-C3N4. Compared to Fe3C/CNF prepared without g-C3N4, the Fe-N/CNF catalyst presents an 4e− improved oxygen reduction reaction activity in both alkaline and acidic media. Furthermore, as a cathode in Zn-air batteries, the Fe-N/CNF catalyst exhibits high performance with an open-circuit voltage of 1.49 V, a power density of 146 mW cm−2 and a specific capacity of 703 mAh g−1. This work suggests a way to prepare metal-nitrogen-carbon catalysts for energy-related electrocatalytic applications.
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Key words:
- Electrospun /
- Carbon nanofiber /
- Oxygen reduction reaction
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Figure 3. (a) TEM, (b) SEM, (c) STEM, (d) High-resolution STEM, (e) element mapping of Fe/CNFs. (f) SEM and (g) TEM images of Fe3C/CNFs
Figure 4. (a) XPS full scan spectrum, (b) high-resolution N1s spectrum and (c) high-resolution Fe2p spectrum of Fe/CNFs. (d) XPS full scan spectrum, (e) high-resolution N1s spectrum and (f) high-resolution Fe2p spectrum of Fe3C/CNFs
Figure 5. (a) CV curves, (b) LSV curves under various rotation speeds (400, 625, 900, 1225, 1600, 2025, 2400 r min−1) and (c) K-L plots of Fe/CNFs. (d) LSV curves, (e) Half-wave potentials and limiting current densities and (f) Tafel slopes of Fe/CNFs, Fe3C/CNFs and Pt/C
Figure 6. (a) CV curves, (b) LSV curves under various rotation speeds (400, 625, 900, 1225, 1600, 2025, 2400 r min−1) and (c) K-L plots of Fe/CNFs. (d) LSV curves, (e) Half-wave potentials and limiting current densities and (f) Tafel slopes of Fe/CNFs, Fe3C/CNFs and Pt/C
Figure 7. (a) Illustration of the basic configuration of the primary ZAB using Fe/CNFs. (b) Open-circuit potential (OCP), (c) polarization and power density curves ans (d) specific capacities of ZABs at 20 mA cm−2 using Pt/C and Fe/CNFs as ORR catalysts
Table 1. The elemental compositions from XPS in Fe/CNFs and Fe3C/CNFs
Sample C N O Fe Fe/CNFs 72.06% 6.90% 19.41% 1.63% Fe3C/CNFs 94.98% 1.88% 2.81% 0.24% 
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