Elsevier

Advanced Powder Technology

Volume 30, Issue 10, October 2019, Pages 2285-2292
Advanced Powder Technology

Original Research Paper
A facile synthesis of α-Ni(OH)2-CNT composite films for supercapacitor application

https://doi.org/10.1016/j.apt.2019.07.008Get rights and content

Highlights

  • α-Ni(OH)2-CNT composite films have been deposited by variation of CNT.

  • Structural, compositional, morphological, and wettability properties of α-Ni(OH)2-CNT composite films.

  • Electrochemical properties of α-Ni(OH)2-CNT composite films.

  • Effect of CNT variation on supercapacitive properties of α-Ni(OH)2-CNT composite films.

Abstract

The α-Ni(OH)2-CNT composite films have been successfully synthesized by a simple chemical method and their supercapacitive properties were investigated by variation of CNT. The structural, compositional, morphological, wettability and electrochemical properties of the composite films were studied by using various characterization techniques. X-ray diffraction analysis revealed that the synthesized composite films are polycrystalline in nature. FT-Raman spectroscopy result showed the characteristic Raman band of CNT and α-Ni(OH)2 which confirmed the formation of α-Ni(OH)2-CNT composite. SEM micrographs showed porous microstructure of the synthesized films and hydrophilic nature of the films was confirmed from wettability studies. Furthermore, the effect of the variation of CNT on the electrochemical properties of the synthesized composite films was discussed. The electrochemical performance of the composite films was studied by using cyclic voltammetry (CV) and Galvanostatic charge–discharge (GCD) techniques. The α-Ni(OH)2-CNT composite showed highest specific capacitance of 544 F g−1 with high retention capability of 85% after 1500th cycle and excellent cycling stability.

Introduction

Electrochemical supercapacitor has raised a great attention for high power energy storage applications because of their excellent cycling strength and high power density [1], [2]. Also, it store energy in the form of electric charges which are environmentally friendly. Depending upon the charge storage mechanism, supercapacitor can be divided into two type’s viz electrochemical double layer capacitor (EDLC) and pseudocapacitor [1], [3]. However, pseudocapacitor has been extensively focused as compared to EDLC owing to their high specific capacitance [2]. The various pseudocapacitive materials, such as transition metal oxides/hydroxides like RuO2, MnO2, NiO, Ni(OH)2, and Co(OH)2 has been successfully used as electrode materials for supercapacitor applications [4], [5], [6], [7], [8]. Among these materials, Ni(OH)2 has been widely studied for supercapacitor applications by reason of its high theoretical specific capacitance, relatively good chemical stability and environmentally friendly nature [9]. But still have limitations in practical applications because of its low energy density (ED) and low electrical conductivity. By considering these limitations, the development of new advanced composite electrode material for supercapacitor applications is a need of an hour. Recently, carbon based materials are extensively used for electrochemical capacitor applications to enhance their supercapacitive performance. It ranges from activated carbon (AC) to carbon nanotube (CNT) [10], [11], [12]. Especially, CNT has been found to be an excellent form of carbon over the other carbonaceous materials and have attracted an extensive attention to prepare composite with metal oxides/hydroxides for supercapacitor electrodes because of its high electrochemically accessible surface area, excellent chemical stability and low resistivity [13], [14]. Additionally, CNT is used to alter the physical properties of metal oxides that are used for various applications such as solar cells [15], electrochromism [16], electrochemical sensors [10] and supercapacitors [17], respectively.

M. Kazazi et al. [18] have prepared nanoflakes nickel oxide-carbon nanotube (NiO-CNT) composite thin films by electrophoretic deposition for high-performance pseudocapacitor applications. They have reported that the prepared NiO-CNT composite electrode exhibited excellent pseudocapacitive behavior with a high specific capacitance of 786 F g−1 and 89.8% of capacitance retention after 1000th cycles as compared to pure NiO electrode. They have concluded that the uniformly dispersed CNT in the electrode that can provide fast and easy conductive pathway for transport of electrons into the active area of electrode material. Cheng et al. [17] have facile synthesized Ni(OH)2/CNTs nanoflake composites, which showed improved performance for supercapacitor applications and gives a specific capacitance of 720 F g−1. They have reported the better progress in electrochemical performance due to the synergetic effect of hydroxides and CNTs. Dai et al. [19] have synthesized CNT-NiO nanocomposite by chemical conversion route and exhibited the high specific capacitance of 759 F g−1 in 6 M KOH electrolyte due to the synergistic effects.

In the present manuscript, a simple chemical bath deposition (CBD) technique is used for the preparation of nickel hydroxide powder. After that an easy and cost-effective doctor blade method is used for the synthesis of α-Ni(OH)2-CNT composite films and their supercapacitive properties have reported. Such an easily synthesized electrode gives the high specific capacitance with remarkable rate ability and excellent cycling strength in 1 M KOH electrolyte. Also, the effect of CNT variation on the electrochemical properties of the as-prepared α-Ni(OH)2-CNT composite films is studied systematically and reported.

Section snippets

Synthesis of α-Ni(OH)2-CNT composite films

The chemicals were of analytical grade (AR) used without further purification. Multi-walled carbon nanotube (MWCNT) was purchased from Monad Nanotech Pvt. Ltd., Mumbai, and used without further purification. For preparation of the precursor solution, double-distilled water (DDW) was used. Scheme 1 represents the steps involved for the synthesis of flower like microstructure α-Ni(OH)2-CNT composite film. Initially, the nickel hydroxide powder was prepared by using chemical bath deposition (CBD)

XRD studies

Fig. 1(a–d) shows the XRD patterns of NC-1, NC-2, NC-3 and NC-4 composite films respectively. It clearly shows that all the films are polycrystalline in nature. The diffraction peaks are located at 12.2°, 33.5°, and 59.6°, along the (0 0 3), (1 0 1) and (1 1 0) planes respectively, which clearly corroborates the structure of pure α-Ni(OH)2 phase [18]. Furthermore, the observed and calculated ‘d’ values of diffraction peaks for α-Ni(OH)2 are matched well with standard JCPDS card no. 38-0715.

Conclusions

A flowerlike porous microstructure of α-Ni(OH)2-CNT composite films have been synthesized by a simple and inexpensive doctor blade method. The composite films showed excellent supercapacitor properties in 1 M KOH electrolyte. X-ray diffraction analysis showed that the composite films are polycrystalline in nature. FT-Raman analysis confirms the well formation of α-Ni(OH)2-CNT composite. Morphological studies shows porous microstructure of the synthesized films and the wettability studies shows

Acknowledgements

The authors gratefully acknowledge to Physics Instrumentation Facility Centre (PIFC), Department of Physics, Shivaji University Kolhapur for various characterization purposes. One of the author C. E. Patil wishes to acknowledge to UGC, New Delhi for financial support through F. No. 41-885/2012 (SR).

References (39)

Cited by (28)

View all citing articles on Scopus
1

Co-corresponding author.

View full text