Single-Nanowire Electrochemical Probe Detection for Internally Optimized Mechanism of Porous Graphene in Electrochemical Devices

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• 作者：Ping Hu ; Mengyu Yan ; Xuanpeng Wang ; Chunhua Han ; Liang He ; Xiujuan Wei ; Chaojiang Niu ; Kangning Zhao ; Xiaocong Tian ; Qiulong Wei ; Zijia Li ; Liqiang Mai
• 刊名：Nano Letters
• 出版年：2016
• 出版时间：March 9, 2016
• 年：2016
• 卷：16
• 期：3
• 页码：1523-1529
• 全文大小：489K
• ISSN：1530-6992

文摘

Graphene has been widely used to enhance the performance of energy storage devices due to its high conductivity, large surface area, and excellent mechanical flexibility. However, it is still unclear how graphene influences the electrochemical performance and reaction mechanisms of electrode materials. The single-nanowire electrochemical probe is an effective tool to explore the intrinsic mechanisms of the electrochemical reactions in situ. Here, pure MnO₂ nanowires, reduced graphene oxide/MnO₂ wire-in-scroll nanowires, and porous graphene oxide/MnO₂ wire-in-scroll nanowires are employed to investigate the capacitance, ion diffusion coefficient, and charge storage mechanisms in single-nanowire electrochemical devices. The porous graphene oxide/MnO₂ wire-in-scroll nanowire delivers an areal capacitance of 104 nF/μm², which is 4.0 and 2.8 times as high as those of reduced graphene oxide/MnO₂ wire-in-scroll nanowire and MnO₂ nanowire, respectively, at a scan rate of 20 mV/s. It is demonstrated that the reduced graphene oxide wrapping around the MnO₂ nanowire greatly increases the electronic conductivity of the active materials, but decreases the ion diffusion coefficient because of the shielding effect of graphene. By creating pores in the graphene, the ion diffusion coefficient is recovered without degradation of the electron transport rate, which significantly improves the capacitance. Such single-nanowire electrochemical probes, which can detect electrochemical processes and behavior in situ, can also be fabricated with other active materials for energy storage and other applications in related fields.