Abstract
Hydrothermal method was adapted to synthesis NiCo
2
O
4
nanoparticles by varying nickel and cobalt precursor concentration as 1:1, 1:2, and 1:3 ratios. X-ray diffraction (XRD) results revealed the spinel NiCo
2
O
4
structure belongs to
Fd
3
¯
m
space group system with face-centered cubic crystal structure. Raman characteristic peaks observed at 495 and 654 cm
−1
explored E
g
and A
2g
modes of spinel NiCo
2
O
4
product. Photoluminescence (PL) results revealed the hole recombination of Ni
2+
/Co
2+
ions from 3d-E
g
and 3d-T
g
electronic state of spinel NiCo
2
O
4
material. The characteristic Fourier transform infrared spectroscopy (FTIR) metal–oxygen bands appeared at 658 and 558 cm
−1
revealed the spinel-type crystal structure. SEM image revealed the NiCo
2
O
4
spherical nanoparticles formation with an average particle size of around 500 nm. The cyclic voltammetry studies revealed the estimated average specific capacitance value of NC3 (NiCo
2
O
4
spherical nanoparticles) as 542 F g
−1
relatively higher than NC1 and NC2. The electro impendence spectroscopy results explored the small arc formation in high frequency range and very low charge transfer resistance (
R
ct
), which resulted high conductive active materials. The estimated specific capacitance for NC3 exhibited superior galvanstatic charging and discharging (GCD) characteristics with high specific capacitance of 294 F g
−1
at high current density of 1 A g
−1
and revealed that the obtained electrode is suitable for supercapacitor applications.
Graphical abstract
Hydrothermal synthesis using an excess of Co source leads to smaller and more uniform particle size. This particle size and the slightly larger crystallite size formed in the materials leads to the improved electrochemical performance of the particles.