Abstract
Hybrid materials play an essential role in the development of the energy storage technologies since a multi-constituent system merges the properties of the individual components. Apart from new features and enhanced performance, such an approach quite often allows the drawbacks of single components to be diminished or reduced entirely. The goal of this paper was to prepare and characterize polymer-metal hydroxide (polypyrrole-nickel hydroxide, PPy-Ni(OH)2) nanowire arrays demonstrating good electrochemical performance. Nanowires were fabricated by potential pulse electrodeposition of pyrrole and nickel hydroxide into nanoporous anodic alumina oxide (AAO) template. The structural features of as-obtained PPy-Ni(OH)2 hybrid nanowires were characterized using FE-SEM and TEM analysis. Their chemical composition was confirmed by energy-dispersive x-ray spectroscopy (EDS). The presence of nickel hydroxide in the synthesized PPy-Ni(OH)2 nanowire array was investigated by X-ray photoelectron spectroscopy (XPS). Both FE-SEM and TEM analyses confirmed that the obtained nanowires were composed of a polymer matrix with nanoparticles dispersed within. EDS and XPS techniques confirmed the presence of PPy-Ni(OH)2 in the nanowire array obtained. Optimal working potential range (i.e., available potential window), charge propagation, and cyclic stability of the electrodes were determined with cyclic voltammetry (CV) at various scan rates. Interestingly, the electrochemical stability window for the aqueous electrolyte at PPy-Ni(OH)2 nanowire array electrode was remarkably wider (ca. 2 times) in comparison with the non-modified PPy electrode. The capacitance values, calculated from cyclic voltammetry performed at 20 mV s−1, were 25 F cm−2 for PPy and 75 F cm−2 for PPy-Ni(OH)2 array electrodes. The cyclic stability of the PPy nanowire array electrode up to 100 cycles showed a capacitance fade of about 13%.
Highlights
The research on the new energy-related materials (NERM) appears to be very significant that the energy demand and consumption is rapidly increasing
In order to obtain Ni(OH)2 nanoparticles dispersed in a polypyrrole network, short cathodic pulses should be applied during electrodepositions
The morphology of hybrid PPy-Ni(OH)2 nanowires was characterized by SEM and transmission electron microscopy (TEM) analyses, which confirmed the existence of metal hydroxide nanoparticles dispersed inside the PPy matrix
Summary
The research on the new energy-related materials (NERM) appears to be very significant that the energy demand and consumption is rapidly increasing. It is widely accepted that conventional materials, based on the various oxides, conducting polymers, and hybrid materials, need to be re-designed at the nano-scale in order to fully exploit their electrochemical potential [1]. Quite often, such manipulation allows the negative impact of the diffusion to be reduced and rate capability to be improved [2,3]. While low-temperature fuel cells and batteries (like Li-ion or Ni-MH) are characterized by low power (up to 2 kW kg−1) and high energy density (up to 1 kWh kg−1), electrochemical capacitors may deliver a power density of 100 kW kg−1 at an energy density usually up to 15 Wh kg–1 [4]. Notwithstanding, ECs might greatly complement other energy storage devices like batteries, protecting them against current fluctuations (at high power demand) and prolonging the system lifetime
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