Synergistic effects of microstructures and active nitrogen content on the oxygen reduction reaction performance of nitrogen-doped carbon nanofibers via KOH activation heat treatment

• Published in: Journal of materials science 2020-08, Vol.55 (24), p.10725-10739
• Main Authors: Shenggao, Wang, Wen, Hu, Mingchen, Zhou, Yuan, Gao, Quanrong, Deng, Yangwu, Mao, Qinfang, Xu, Geming, Wang
• Format: Article
• Language: English
• Subjects: Activation; Adsorption; Analysis; Carbon fibers; Catalysts; Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; Crystallography and Scattering Methods; Diffraction; Electrocatalysts; Electron transfer; Emission analysis; Energy Materials; Field emission microscopy; Force and energy; Heat treating; Heat treatment; Materials Science; Nanofibers; Nitrogen; Oxygen reduction reactions; Photoelectrons; Polyacrylonitrile; Polymer Sciences; Solid Mechanics; Synergistic effect; X-ray spectroscopy; X-rays
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-020-04673-9

A series of nitrogen-doped carbon nanofibers (N-CNFs) have been successfully synthesized via electrospinning N , N -dimethylformamide/polyacrylonitrile followed by KOH activation heat treatment. The electrocatalysts are thoroughly studied with X-ray diffraction, field emission scanning electron microscope, transmission electron microscopy, nitrogen adsorption–desorption isotherms, X-ray photoelectron spectroscopy, respectively, and electrochemical method. The time of KOH activation heat treatment is found to yield a considerable effect on crystallinity, microstructure, chemical surface states, the total content of nitrogen and the active nitrogen configurations in all samples. The resulting N-CNFs-3.0 h catalyst shows remarkable advantages for ORR performance, including porous microstructures, high specific surface area, abundant exposed active sites and high content of ORR-active pyridinic-N. With these favorable features, N-CNFs-3.0 h exhibits an overall distinguished ORR performance in alkaline media compared to commercial 20 wt% Pt/C catalyst, which has a high onset potential of 0.9 V (vs. RHE), half-wave potential of 0.83 V (vs. RHE) and electron transfer number (3.93). The superior ORR of N-CNFs-3.0 h mainly originates from the synergistic effect of porous microstructures and high ORR-active pyridinic-N content, which could be optimized by changing KOH activation time. This work presents a facile strategy to controllably design and fabricate highly active ORR metal-free carbon-based electrocatalysts.