Hybrid composite polyaniline-nickel hydroxide electrode materials for supercapacitor applications

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.