Sol-gel synthesized nickel oxide nanostructures on nickel foam and nickel mesh for a targeted energy storage application

Abstract

The nickel-based oxides are treated as favourable pseudocapacitive electrode materials for energy storage application owing to their inexpensive nature, well-defined redox activity, as well as liberty in tuning the microstructures by changing the synthesis process optimizing its vital parameters. However, a real challenge for fabricating nickel-based materials is to sustain the uniform morphology onto a conductive substrates like FTO, ITO, stainless steel, nickel foam, nickel mesh, and copper foam etc. Herein, nickel oxide (NiO) nanostructures (NSs) with high pseudocapacitive performance have been prepared via the sol-gel technique for energy storage application. The structural identity of NiO-NSs is documented by X-ray diffraction, which confirmed the monoclinic crystal structure of the synthesized NSs. The X-ray photoelectron spectroscopy confirmed the valence state of the nickel as ‘+2′ and oxygen as ‘-2′. The field-emission scanning electron microscopy of NiO-NSs revealed non-uniform large spherical clusters agglomerated onto the surface. The NiO-NSs manifested the mesoporous channels and exhibit a surface area of 31.4 m2g-1, which is evaluated through Brunauer-Emmett-Teller analysis. The fabricated NiO-nickel foam (NF) electrode exhibit a high specific capacitance of 871 Fg−1 at a scan rate of 5 mVs−1 in 4 M KOH solution. Moreover, the NiO−NF electrode displayed the cyclic retention of 86.5 % after 10,000 cycles. The mesoporous channels of the electrode material afford plentiful, accessible, active sites to the effective charge transportation of electrolyte charges over the electrolyte-electrode interface and boost the electrochemical performance of NiONF −electrodes. Moreover, an asymmetric supercapacitor device constructed with NiO−NF as the anode and AC−NF as the cathode delivers high specific energy and specific power (24 Whkg−1 at 2.9 kWkg−1), and good cycling stability (retention of 89.7 % over 5 000 cycles)