Co nanoparticle embedded in atomically-dispersed Co-N-C nanofibers for oxygen reduction with high activity and remarkable durability

• Published in: Nano energy 2018-10, Vol.52, p.485-493
• Main Authors: Cheng, Qingqing, Han, Shaobo, Mao, Kun, Chen, Chi, Yang, Lijun, Zou, Zhiqing, Gu, Meng, Hu, Zheng, Yang, Hui
• Format: Article
• Language: English
• Subjects: Embedded Co nanoparticle; Long-term durability; Oxygen reduction reaction; Proton exchange membrane fuel cell; Single Co atom
• ISSN: 2211-2855
• DOI: 10.1016/j.nanoen.2018.08.005

Although Co and N codoped carbon (Co-N-C) materials could be served as the promising oxygen reduction reaction (ORR) electrocatalysts, they still suffer from unsatisfactory catalytic activity, especially in acidic environment. Herein, we report that the construction of Co nanoparticles embedded within highly porous, atomically-dispersed Co-N-C nanofibers catalyst not only significantly improves the ORR activity with a half-wave potential (E1/2) of 0.778 V/RHE, but also achieves the remarkable durability with only ~ 9 mV decay of E1/2 after a 10000-cycle accelerated durability test between 0.6 and 1.1 V. Both aberration-corrected scanning transmission electron microscope and X-ray adsorption spectroscopy confirm the existence of Co single atoms in the carbon nanofibers. Density functional theoretical calculation reveals that the introduction of Co core nanoparticle lowers the d band center of surface Co atoms in graphite shells and makes the free energy diagrams of the ORR process on Co-N-C shell more close to the ideal case, thus boosting the catalytic performance. Proton exchange membrane fuel cell integrated with as-prepared catalyst delivers a peak power density of 0.42 W cm−2 together with excellent stability after 100 h operation. This study provides an ideal perspective to develop highly efficient and durable Co-based catalyst for the oxygen reduction. The atomically-dispersed Co-N doped carbon shell encapsulation on Co nanoparticles structure exhibits outstanding ORR activity together with excellent durability in proton exchange membrane fuel cells. [Display omitted] •This Co@SACo-N-C nanofiber catalyst is developed through electrospinning, pre-carbonization and ammonium etching process.•Both aberration-corrected STEM and X-ray adsorption spectroscopy confirm the existence of single Co atom.•The prepared catalyst exhibits high activity and excellent durability towards ORR in acidic solution.•DFT reveals that the Co nanoparticle core lowers the d band center of Co-N active sites, thus boosting the ORR performance.