Abstract
A green and sustainable approach to recycle the waste iron rust into a valuable α modification of Fe2O3 via simple grinding and calcination for application in a hybrid supercapacitor is reported. The α-Fe2O3 was coupled with carbon nanofibers (CNFs) and conducting polymer, polyaniline (PANI), to form composite hybrid supercapacitor electrode materials. The conventional hydrothermal, electrospinning, and in-situ polymerization processes were used to prepare composites. Further, X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), and energy-dispersive x-ray (EDAX) spectroscopy were used to study the structural, morphological, and compositional properties of the as-synthesized α-Fe2O3 and its composites with CNF and PANI. The α-Fe2O3/CNF and α-Fe2O3/PANI composites, coated on carbon rod, were used as electrodes in a three-electrode system to study electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge–discharge (GCD) in 1 M H2SO4. The XRD studies revealed the formulation of iron rust into α-Fe2O3 modifications with an average of 28 nm crystallite size. Uniform dispersion of α-Fe2O3 over CNF of 400–500 nm diameter and excellent covering of PANI over α-Fe2O3 nanomaterials were the morphological features observed for α-Fe2O3 /CNF and α-Fe2O3 /PANI composites, respectively. The electrochemical studies on α-Fe2O3/PANI composites exhibit higher performance as against Fe2O3/CNF with respect to specific capacitance, 192 Fg−1 (88.88 Fg−1); energy density, 11.28 Whkg−1 (3.084 Whkg−1); power density, 162 Wkg−1 (69.39 Wkg−1); and capacitance retention of 80% (75%) after 5000 charge–discharge cycles. The heavy dispersion of α-Fe2O3 over long CNF and PANI fibers with intimate contact resulted in abundant active sites for electrochemical reactions leading to the obtained result. The rust-derived α-Fe2O3 with PANI offers excellent stability to act as a potential candidate for sustainable hybrid supercapacitor application.
Highlights
The past few decades have witnessed a rapid development in industrial automation, transportation and huge upsurge of modern household appliances
Supercapacitor have emerged as an eco-friendly and safe means of energy storage device due to its characteristics such as comparatively small size, high power density (5-10 kWkg-1), long cycle life (>5,00,000 cycles), long shelf life, high efficiency (95%), wide operating temperature range (-40 to +70 C) etc
Graphite rod coated with a slurry, prepared by mixing αFe2O3/carbon nanofibers (CNF) or Poly aniline (PANI): Poly Vinylidene Difluoride (PVDF): Carbon black taken in 85:10:5 ratio was used as electrodes
Summary
The past few decades have witnessed a rapid development in industrial automation, transportation and huge upsurge of modern household appliances. One of the methods, electrospinning method, working under the precisely controlled conditions, has emerged as a versatile, efficient, continuous and industrially viable method to evolve long nanofibers with different morphology having extremely high aspect ratio and large surface area to volume ratio [10] Such fibers are highly desirable for use in energy storage applications since they exhibit transportation directionally and short ionic transport lengths [11]. A good number of literature is available wherein a thermodynamically stable form of iron oxide, α-Fe2O3 (Hematite), coupled with carbon nano fiber via methods like hydrothermal [25,26,27], electrospinning [28,29], vapour growth [30], gel templating [31] and mechanical press [32] has been utilized as efficient negative electrode in Li ion/ Na ion batteries and or as supercapacitor in the potential range from -1.2 to 0 V. The as synthesised αFe2O3 was further coupled with CNF and PANI to get binary positive electrode material
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More From: Journal of Materials Science: Materials in Electronics
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