Izan Izwan Misnon

Superior supercapacitive performance in electrospun copper oxide nanowire electrodes

Copper oxide (CuO) nanowires of diameter ∼30–50 nm were developed by an aqueous polymeric solution based electrospinning process and their structural, morphological, and electrochemical properties were studied with the aim to fabricate high performance supercapacitor devices. The wires consist of densely packed cuboidal particles of size ∼10 nm characterized by a low degree of crystal defects. Supercapacitor electrodes were fabricated on nickel foam substrates using 75 wt% CuO in 15 wt% conducting carbon and 10 wt% polyvinylidene fluoride. The supercapacitive properties of the electrodes were evaluated in a three-electrode configuration in aqueous electrolytes, viz. KOH and LiOH, employing cyclic voltammetry (CV), charge–discharge cycling (CDC) and electrochemical impedance spectroscopy (EIS). A record specific capacitance (CS) is observed for the present electrospun CuO nanowires: CS ∼ 620 F g−1 in KOH and 581 F g−1 in LiOH at a current density of 2 A g−1 with a Coulombic efficiency of ∼100%. Compared with the previous results on the electrochemical stability of CuO nanostructures, the material electrospun using an aqueous polymeric solution showed a much higher operational stability (98% at the end of 1000 cycles and 92% at the end of 2000 cycles) owing to its superior crystallinity. The electrochemical properties of the electrodes were determined using EIS to validate the CV and CDC results.

One-Dimensional Assembly of Conductive and Capacitive Metal Oxide Electrodes for High-Performance Asymmetric Supercapacitors

A one-dimensional morphology comprising nanograins of two metal oxides, one with higher electrical conductivity (CuO) and the other with higher charge storability (Co3O4), is developed by electrospinning technique. The CuO-Co3O4 nanocomposite nanowires thus formed show high specific capacitance, high rate capability, and high cycling stability compared to their single-component nanowire counterparts when used as a supercapacitor electrode. Practical symmetric (SSCs) and asymmetric (ASCs) supercapacitors are fabricated using commercial activated carbon, CuO, Co3O4, and CuO-Co3O4 composite nanowires, and their properties are compared. A high energy density of ∼44 Wh kg-1 at a power density of 14 kW kg-1 is achieved in CuO-Co3O4 ASCs employing aqueous alkaline electrolytes, enabling them to store high energy at a faster rate. The current methodology of hybrid nanowires of various functional materials could be applied to extend the performance limit of diverse electrical and electrochemical devices.

Synthesis and electrochemical evaluation of the PANI/δ-MnO2 electrode for high performing asymmetric supercapacitors

A comprehensive analysis of the effect of in situ polymerization of polyaniline (PANI) on hydrothermally synthesized Birnessite-type MnO2 (δ-MnO2) flowers on the structural, surface, morphological, and electrochemical properties is presented in this article. The PANI–MnO2 electrodes showed ∼170% higher specific capacitance than pure MnO2; the factors contributing to this enhancement are systematically investigated and discussed. The PANI modification enabled the inactive surface of the MnO2 to be electrochemically active and reduced the characteristic resistances and charge relaxation time. Furthermore, the PANI modification improved the composite conductivity and resulted in (i) reduction of surface pseudocapacitance from 87% (MnO2) to 54% (PANI–MnO2) and (ii) improvement of active charge contribution from 42% (MnO2) to 46% (PANI–MnO2). The mechanism of these changes is discussed. Furthermore, asymmetric (PANI–MnO2//AC and PANI–MnO2//OMC) and symmetric (AC//AC and OMC//OMC) (where AC is activated carbon and OMC is mesoporous carbon) supercapacitors are fabricated in coin cell casing and their charge storage properties are evaluated. Impressive increase in energy storage is observed; however, their properties varied according to the porosity of the carbon electrode. Results from this study provide a better understanding of the charge storage behaviour of polymer coated metal oxide electrodes with a varied choice of carbons in asymmetric supercapacitors.