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MFe 2 O 4 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
Author(s) -
Xiao Junwu,
Xu Guiliang,
Sun ShiGang,
Yang Shihe
Publication year - 2013
Publication title -
particle and particle systems characterization
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.877
H-Index - 56
eISSN - 1521-4117
pISSN - 0934-0866
DOI - 10.1002/ppsc.201300105
Subject(s) - graphene , oxide , nanostructure , materials science , lithium (medication) , nanoparticle , electron transfer , chemical engineering , nanotechnology , conductivity , chemistry , metallurgy , organic chemistry , medicine , endocrinology , engineering
The intrinsically low electric conductivity and self‐aggregation of MFe 2 O 4 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 2 O 4 nanoparticles and rapidly shuttle electrons to and from the MFe 2 O 4 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 2 O 4 allows the composites to exhibit the comparable specific capacity (based on the total mass) to MFe 2 O 4 , although over 10 wt% of NGS contributes a low specific capacity of around 320–400 mAh g −1 . More importantly, introducing NGS significantly increases the cycling stability performance: 97.5% (CoFe 2 O 4 /NGS) and ≈100% (NiFe 2 O 4 /NGS) of the specific capacities have been retained after 80 cycles, far higher than the capacity retentions of CoFe 2 O 4 (35.3%) and NiFe 2 O 4 (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 2 O 4 nanoparticles are transformed into metal@oxide core–shell nanostructure, mainly because the core–shell nanostructure exhibits lower charge transfer resistance.