Synthesis of graphene/nickel oxide composite with improved electrochemical performance in capacitors
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ORIGINAL PAPER
Synthesis of graphene/nickel oxide composite with improved electrochemical performance in capacitors Feng Gao & Qing Wei & Jiaxiang Yang & Hong Bi & Mingtai Wang
Received: 29 January 2013 / Revised: 10 June 2013 / Accepted: 10 June 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract A novel reduced graphene oxide/NiO nanosheet composite (r-GO/NiO) (ca. 75 % NiO in weight) was synthesized by a facile two-step method, where the NiO nanosheets were decorated with some voids. The composite was characterized by using X-ray diffraction, transmission electron microscopy, thermal gravimetric analysis, and Raman spectroscopy. The electrochemical properties of the composite were investigated by cyclic voltammetry, galvanostatic charge, and discharge measurements. The results show that the r-GO/NiO composite exhibits a stable average specific capacitance of ca. 1,139 F g−1 (at 0.5 A g−1) during 1,000 charge–discharge cycles, suggesting that the r-GO/NiO composite is a potential supercapacitor material. The main correlation between the electrochemical performance and the structure of the materials was studied, and the formation process of the composite was also discussed. Keywords Nickel oxide . Carbon materials . Graphene oxide . Composite . Supercapacitor
Introduction Graphene, an atomically thick two-dimensional carbon material, has been of great interest due to its unique electronic, F. Gao : Q. Wei : J. Yang : H. Bi College of Chemistry and Chemical Engineering, Anhui University, Hefei 230039, People’s Republic of China F. Gao : Q. Wei : J. Yang : H. Bi (*) Key Laboratory of Environment-Friendly Polymer Materials of Anhui Province, Anhui University, Hefei 230039, People’s Republic of China e-mail: [email protected] M. Wang Institute of Plasma Physic, Chinese Academy of Sciences, Hefei 230031, People’s Republic of China
thermal, mechanical, and chemical properties [1, 2]. Two derivatives can be distinguished from graphene, that is, graphene oxide (GO) and reduced graphene oxide (r-GO). GO can be practically referred to as a functionalized graphene with various oxygen-bearing groups (e.g., C=O, C–O, and –OH), while r-GO is normally obtained through chemical reduction of GO [2, 3]. Nanocomposites of graphene and metal oxides have been successfully prepared on the basis of either GO or r-GO, such as GO/TiO2 [4], GO/nickel oxide (NiO)x [5, 6], r-GO/TiO2 or r-GO/SnO2 [7], r-GO/ZnO [8], and GO/Ni(OH)2 [9]; those hybrids were used as an effective photocatalyst [7], sensor [10], and photovoltaic material [5]. As NiO is a promising capacitor material [11–14], considerable efforts have been attempted to synthesize graphene/NiO composites for capacitors [15–18], but their specific capacitance is normally lower than 600 F g−1. Wang et al. [19] recently reported r-GO/NiO sheet-on-sheet composite from the calcination of rGO/Ni(OH)2 precursor in air and obtained a stable charge capacity of 1,031 mAh g−1 (at 0.1 °C) after 40 charge– discharge cycles in Li battery application; Duan et al. [20] reported the synthesis
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