Abstract
Over recent decades, the conversion of energy and its storage have been in the lime light due to the depletion of fossil resources. The electrochemical energy storage devices like supercapacitors and batteries, and their materials and fabrication methods have been extensively evaluated, which is the best solution for the energy crisis. Herein, zinc cobaltite (ZnCo2O4; ZCO) nanostructures grown on nickel (Ni) foam by microwave-assisted solvothermal fabrication for hybrid supercapacitors are reported. Two different structures/samples, ZCO-15/Ni (nanoflowers) and ZCO-30/Ni (nanowires), were obtained by simply adjusting the reaction time. The electrochemical and physicochemical properties of the as-prepared samples were systematically determined. Particularly, ZCO-15/Ni exhibits excellent structural stability due to its dual morphologies: nanoflowers and nanopetals, and exhibits a large electroactive surface area (25.61 m2 g−1), pore diameter (48.38 nm), and robust adhesion to Ni foam, enabling ion and electron transport. ZCO-15/Ni foam electrode delivers an excellent specific capacity of 650.27 C g−1 at 0.5 A g−1 and admirable cyclic performance of 91% capacitance retention after 5000 cycles compared to ZCO-30/Ni electrode. The excellent electrochemical performance of ZCO makes them promising electrode materials for batteries, hybrid supercapacitors, and other alternative energy storage applications.
Highlights
Environmental change and consumption of petroleum products have unequivocally impacted the normal biological system and human economies
The ZCO nano owers on Ni foam exhibited a large integral area indicated by the CV curve, higher time response from the GCD curves, and lower internal and charge-transfer resistance, which leads to high electrochemical performance compared to others
To examine the electrochemical activity of ZCO-15/Ni and ZCO-30/Ni, we investigated the relation between peak current density (i) and scan rate (v) and followed a power law.[43,44] i 1⁄4 avb where ‘a’ and ‘b’ are variable parameters; when b 1⁄4 0.5, the electrochemical process is diffusion controlled, and when b 1⁄4 1, the electrochemical process is a non-diffusion-controlled surface redox process.[43]
Summary
Of providing a higher power density with an improved long-life than batteries and storing more than the conventional energy storage devices.[7,8,9] Generally energy storage of the SCs depend on ionic adsorption (for electrical double-layer capacitors, EDLCs) or fast surface redox reactions (for pseudocapacitors).[10,11,12] The combined electrode of EDLCs and pseudocapacitors form asymmetric supercapacitors, and they can extend the cell voltage.[13]. In order to improve the electrochemical performance of hybrid supercapacitors, one has to design electrodes with abundant electroactive sites and high transfer rates and for ions of the electrolyte and electrons participating in the faradaic reactions simultaneously.[1,28] Recently, various morphologies of ZCO nano/microstructures on the surface of various conductive substrates like carbon cloth, FTO, ITO, and Ni foam were prepared[29,30] and used directly as integrated electrodes for hybrid supercapacitors. The ZCO nano owers on Ni foam exhibited a large integral area indicated by the CV curve, higher time response from the GCD curves, and lower internal and charge-transfer resistance, which leads to high electrochemical performance compared to others. The authors prepared another sample with similar synthesis conditions except for the microwave reaction time of 30 min and labeled it as ZCO-30/Ni
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
