Hybrid composite polyaniline-nickel hydroxide electrode materials for supercapacitor applications

Janardhan H Shendkar,Vijaykumar V Jadhav,Pritamkumar V Shinde,Rajaram S Mane,Colm O'Dwyer

doi:10.1016/j.heliyon.2018.e00801

Janardhan H Shendkar, Vijaykumar V Jadhav + Show 3 more

Open Access

https://doi.org/10.1016/j.heliyon.2018.e00801

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Abstract

Pristine and nanocomposite (NC) hybrid electrodes of polyaniline (PANI)-nickel hydroxide [Ni(OH)2] have been prepared by single and two-step electrodeposition processes, respectively, onto stainless-steel (SS) substrates. Enhanced reversibility and stability of amorphous PANI- Ni(OH)2 NC electrodes compared to single electrode materials have been explored. PANI has a nanofibrous morphology, Ni(OH)2 has nanoplatelet-type morphology, and the NC electrodes retain an overall nanofibrous morphology. The maximum specific capacitance (SC), obtained from integrated charge under voltammetric conditions, for PANI (electro-deposited for 5 min), NC (electrodeposition of Ni(OH)2 for 10 min and 20 min onto PANI electrode surface) and Ni(OH)2 (electrodeposited for 10 min) electrodes, are 0.59, 39.06, 32.36, and 113.8 F/g, respectively, suggesting higher electrochemical performance of Ni(OH)2 electrode compared to PANI and NC electrodes. The retention in SC values with faster scan rates from 10 to 100 mV/s for PANI, NC (10 min), NC (20 min) and Ni(OH)2 are 38.7, 61.1, 52.4, and 29.0 %, respectively, explicitly confirming a higher reversibility in NC electrodes. The retention in SC values with increase of cycle number up to 1000 for PANI, NC (10 min), NC (20 min) and Ni(OH)2 electrodes are 34.9, 61.5, 67.5, and 40.7 % respectively, demonstrating higher electrochemical stability of NC electrodes over pure-phase electrodes. Nearly 2.15, 79.36, 66.66 and 406.83 mC/cm2 charges on PANI, NC (10 min), NC (20 min) and Ni(OH)2 electrodes, respectively, are obtained. Inner to total charge and outer to total charge ratios have been used to explain contributing sites to total charge in pristine and NC electrodes.

Highlights

Electrochemical supercapacitors (ES), have attracted considerable attention in recent years, as they are capable of providing a higher power density than batteries, in addition to high energy density compared to traditional capacitors, long cyclability and fast charge/discharge capability, which are useful in miniaturized consumer electronic products such as memory back-up systems, electrical vehicles and industrial power/energy management etc. [1, 2, 3]
We have investigated the structural, morphological, and electrochemical supercapacitive properties of pristine PANI, Ni(OH)2 and PANI-Ni(OH)2 NC electrodes
With completion of lateral growth i.e. a compact layer covering the surface of SS by PANI, the aniline monomer continues to grow vertically in 1D on the already present active nuclei sites in compact layer instead of forming new nuclei to form 2D planar thin film-type morphology

Summary

Introduction

Electrochemical supercapacitors (ES), have attracted considerable attention in recent years, as they are capable of providing a higher power density than batteries, in addition to high energy density compared to traditional capacitors, long cyclability and fast charge/discharge capability, which are useful in miniaturized consumer electronic products (where high operating potential is required and energy density is directly proportional to the square of operating potential window) such as memory back-up systems, electrical vehicles and industrial power/energy management etc. [1, 2, 3]. With well-defined redox activity, low-cost, layered morphology and high SC value, it has been extensively studied over the last few decades [18, 19]. It suffers weak adhesion between the nickel-based material and the current collector (substrate), leading to the loss of active material and short cycle life as an ES electrode [20]. PANI polymerized from aniline in aqueous acidic solution can be converted to several forms with different electrical properties by acid/base treatments and/or oxidation. We have investigated the structural, morphological, and electrochemical supercapacitive properties of pristine PANI, Ni(OH) and PANI-Ni(OH) NC electrodes

Experimental

Results and discussion

Conclusions