Band-correlated barrier-hopping conduction in α-NiMoO₄ micro-crystals and comparison of its energy storage performance with MWCNT-integrated complex

Monoclinic nickel molybdate (NiMoO₄) micro-crystals were synthesized via a conventional solid-state synthesis route with a prospective to investigate its conductivity response with high-temperature evolution and phenomenal electrochemical performance for supercapacitor application. The tenacious phase formation, Raman active phonon vibration and metal oxide (Ni–O, Mo–O) stretching vibration in octahedral and tetrahedral sites of as-synthesized NiMoO₄ were confirmed by X-ray diffraction techniques, Raman and FTIR spectra. The UV-DRS absorbance spectra of NiMoO₄ exhibits several effective absorption peaks in the UV–Visible wavelength range (200–800 nm). The optical band gap of NiMoO₄ was estimated at 2.50 eV experimentally with the famous Kubelka–Munk equation and theoretically correlated with the result obtained from the density of states (DOS) calculation. The saturation magnetization of NiMoO₄ diminished from 0.0026 to 0.0013 emu g⁻¹. significantly due to the embodiment of MWCNT but the coercivity maintain a minute change. Lessening of real (Z′) and imaginary impedance (Z″) with temperature was observed with high-temperature evolution (633–773 K) and the Nyquist plots were well fitted with equivalent circuit model (QR)(QR)(CR) network. The temperature-dependent frequency exponent (n) suggested the band-correlated barrier-hopping process in high temperature for the conduction mechanism of NiMoO₄. The maximum specific capacitance (C_sp) was estimated 518 F g⁻¹ for NiMoO₄ at current density 5 Ag⁻¹ and its value intensified up to 1050 A g⁻¹ at current density 5 Ag⁻¹ in MWCNT-integrated NiMoO₄. Imperatively, the upmost energy density 66.12 Wh Kg⁻¹ was detected at power density 1075 W Kg⁻¹ for MWCNT-blended NiMoO₄ which is significantly larger than pristine NiMoO₄ (energy density 42.28 Wh Kg⁻¹ at power density 612 W Kg⁻¹) at a current density 5 Ag⁻¹, which reveals their great potential application as a supercapacitor and energy storage technology.