MFe2O4 and MFe@Oxide Core–Shell Nanoparticles Anchored on N‐Doped Graphene Sheets for Synergistically Enhancing Lithium Storage Performance and Electrocatalytic Activity for Oxygen Reduction Reactions. (2nd July 2013)

• Record Type: Journal Article
• Authors: Xiao, Junwu; Xu, Guiliang; Sun, Shi‐Gang; Yang, Shihe
• Is Part Of: Particle and particle systems characterization. Volume 30:Number 10(2013:Oct.)
• Page Start: 893
• Page End: 904
• Publication Date: 2013-07-02
• Subjects: Particles -- Periodicals; 620.43
• DOI: 10.1002/ppsc.201300105
• Languages: English
• ISSNs: 0934-0866

Abstract

<abstract abstract-type="main" xml:lang="en"> <title> <x xml:space="preserve">Abstract</x> </title> <p>The intrinsically low electric conductivity and self‐aggregation of MFe<sub>2</sub>O<sub>4</sub> during charge/discharge affect their lithium storage performance and electrocatalytic activity. To mitigate these problems, it is shown that N‐doped graphene sheets (NGS), as a highly conductive platform, finely disperse the MFe<sub>2</sub>O<sub>4</sub> nanoparticles and rapidly shuttle electrons to and from the MFe<sub>2</sub>O<sub>4</sub> nanoparticles. Moreover, by forming a metal@oxide core–shell nanostructure, fast electron transfer from the exterior oxide layer to NGS is achieved. Introducing NGS into MFe<sub>2</sub>O<sub>4</sub> allows the composites to exhibit the comparable specific capacity (based on the total mass) to MFe<sub>2</sub>O<sub>4</sub>, although over 10 wt% of NGS contributes a low specific capacity of around 320–400 mAh g<sup>−1</sup>. More importantly, introducing NGS significantly increases the cycling stability performance: 97.5% (CoFe<sub>2</sub>O<sub>4</sub>/NGS) and ≈100% (NiFe<sub>2</sub>O<sub>4</sub>/NGS) of the specific capacities have been retained after 80 cycles, far higher than the capacity retentions of CoFe<sub>2</sub>O<sub>4</sub> (35.3%) and NiFe<sub>2</sub>O<sub>4</sub> (43.7%) tested under otherwise identical conditions. Also demonstrated are the excellent rate capabilities of the composites. For catalyzing the oxygen reduction reaction, the activity is significantly improved when the MFe<sub>2</sub>O<sub>4</sub> nanoparticles are transformed into metal@oxide core–shell nanostructure, mainly because the core–shell nanostructure exhibits lower charge transfer resistance.</p> </abstract>