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The present study involves the synthesis of a bismuth oxide (BiO) electrode consisting of an arranged nano-platelets for evolving a flower-type surface appearance on nickel-foam (BiO-Ni-F) by a simple, inexpensive, binder-free and one-step chemical bath deposition (CBD) method, popularly known as a wet chemical method. The as-prepared BiO on Ni-foam, as an electrode material, demonstrates 557 F g specific capacitance (SC, at 1 mA cm), of which 85% is retained even after 2000 cycles. With specific power density of 500 kW kg, the BiO-Ni-F electrode documents a specific energy density of 80 Wh kg. Furthermore, a portable asymmetric supercapacitor device, i.e. a pencil-type cell consisting of BiO-Ni-F as an anode and graphite as a cathode in 6 M KOH aqueous electrolyte solution, confirms 11 Wh kg and 720 kW kg specific energy and specific power densities, respectively. An easy and a simple synthesis approach for manufacturing a portable laboratory scale pencil-type supercapacitor device is a major outcome of this study, which can also be applied for ternary and quaternary metal oxides for recording an enhanced performance. In addition, we presented a demonstration of lighting a light emitting diode (LED) using a home-made pencil-type supercapacitor device which, finally, has confirmed the scaling and technical potentiality of BiO-Ni-F in energy storage devices.

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Superfast (≤10 min) room-temperature (300 K) chemical synthesis of three-dimensional (3-D) polycrystalline and mesoporous bismuth(III) oxide (BiO) nanostructured negatrode (as an abbreviation of negative electrode) materials, viz., coconut shell, marigold, honey nest cross section and rose with different surface areas, charge transfer resistances, and electrochemical performances essential for energy storage, harvesting, and even catalysis devices, are directly grown onto Ni foam without and with poly(ethylene glycol), ethylene glycol, and ammonium fluoride surfactants, respectively. Smaller diffusion lengths, caused by the involvement of irregular crevices, allow electrolyte ions to infiltrate deeply, increasing the utility of inner active sites for the following electrochemical performance. A marigold 3-D BiO electrode of 58 m·g surface area has demonstrated a specific capacitance of 447 F·g at 2 A·g and chemical stability of 85% even after 5000 redox cycles at 10 A·g in a 6 M KOH electrolyte solution, which were higher than those of other morphology negatrode materials. An asymmetric supercapacitor (AS) device assembled with marigold BiO negatrode and manganese(II) carbonate quantum dots/nickel hydrogen-manganese(II)-carbonate (MnCOQDs/NiH-Mn-CO) positrode corroborates as high as 51 Wh·kg energy at 1500 W·kg power and nearly 81% cycling stability even after 5000 cycles. The obtained results were comparable or superior to the values reported previously for other BiO morphologies. This AS assembly glowed a red-light-emitting diode for 20 min, demonstrating the scientific and industrial credentials of the developed superfast BiO nanostructured negatrodes in assembling various energy storage devices.

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Sulphur source-inspired self-grown polycrystalline and mesoporous nickel sulfide (Ni x S y ) superstructures with vertically aligned nanomorphologies viz. rods, flakes, buds, and petals, synthesized at elevated temperatures and moderate pressures by a facile one-pot hydrothermal method on a three-dimensional Ni foam demonstrate remarkable areal specific capacitances of 7152, 4835, and 2160 F cm −2 at current densities of 1, 2, and 5 mA cm −2 , respectively, with a cycling stability of 94% for a battery-type electrochemical supercapacitor when used as an electrode material in a supercapacitor. The Ni x S y //Bi 2 O 3 asymmetric supercapacitor assembly exhibits an energy density of 41 W h•kg −1 at a power density of 1399 W kg −1 for 1 A g −1 and was used in a three-cell series combination to operate a "GFHIM" display panel (our research institute name, Global Frontier R & D Center for Hybrid Interface Materials) composed of nearly 50 differently colored light-emitting diodes with high intensity in 1 M KOH water-alkali electrolyte. The electrochemical supercapacitor results obtained for the Ni x S y superstructures because of a combination of catalytically active amorphous and high mobility polycrystalline are highly comparable to those reported previously for salt-mediated and self-grown Ni x S y structures and morphologies.

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