Bridging of Ultrathin NiCo2O4 Nanosheets and Graphene with Polyaniline: A Theoretical and Experimental Study

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• 作者：Juan Yang ; Chang Yu ; Suxia Liang ; Shaofeng Li ; Huawei Huang ; Xiaotong Han ; Changtai Zhao ; Xuedan Song ; Ce Hao ; Pulickel M. Ajayan ; Jieshan Qiu
• 刊名：Chemistry of Materials
• 出版年：2016
• 出版时间：August 23, 2016
• 年：2016
• 卷：28
• 期：16
• 页码：5855-5863
• 全文大小：612K
• 年卷期：0
• ISSN：1520-5002

文摘

Ultrathin inorganic nanosheets that enable fast electrochemical reaction kinetics are highly required in many energy-related applications. Herein, we report a simple strategy for in situ assembly of ultrathin NiCo₂O₄ nanosheets with enriched surface active sites on graphene surface in a vertical orientation way by employing polyaniline (PANI) as the structure coupling bridge between the two components (denoted by NiCo₂O₄–P-G). The as-made ultrathin NiCo₂O₄ nanosheets are rich in metal ions in high valence state and oxygen defective sites, and feature 3D open frameworks with hierarchical pore structure. It has been found that the nitrogen species derived from PANI building blocks as bridging sites tend to bond with metal ions, which effectively tune the electronic structural states and result in strong coupling effects with the NiCo₂O₄ nanosheets. Benefiting from these structural characteristics, the as-made NiCo₂O₄–P-G hybrids, when used as pseudocapacitive electrode materials, can deliver a high specific capacitance of 966 F g^–1 (based on the mass of the active NiCo₂O₄ component) and an excellent rate capability of ca. 84% even the current density increased by 100 times and long-term stability. As the precious metal-free electrocatalyst for the oxygen evolution (OER) reaction, the NiCo₂O₄–P-G hybrids are also able to deliver a low overpotential of 0.32 V at a current density of 10 mA cm^–2 in 0.1 M KOH aqueous electrolyte (only 70% iR compensation), holding promise for high performance yet cheap electrocatalysts for the OER reaction.