A Comparative Study on the Structural and Optical Properties of NiMoO4 Nanomaterials Synthesized by Hydrothermal and Solvothermal Route

In the present work, a transition metal-based ternary oxide of NiMoO₄ nanomaterials is prepared by both hydrothermal and solvothermal methods with various synthesis conditions. Structural evolution as a function of increase in calcination temperature is also discussed. Scanning electron microscope (SEM) analysis presents the surface morphology of as-prepared samples with an apparent change in the particle size under different synthesis conditions. Energy Dispersive X-ray spectroscopy (EDAX) analysis confirms the chemical composition of the nanomaterials. Structural analysis by X-Ray powder Diffraction (XRD) exhibits the formation of 𝛼 and β-phase of NiMoO₄ and further pure 𝛼-phase is observed at calcination temperature of 650 °C. Fourier Transform Infrared spectroscopy (FTIR) indicates various functional groups present in NiMoO₄ sample. UV–vis absorption spectra present a broad peak around 220–450 nm. A direct and indirect energy band gap of ≈2.2 and ≈1.9 eV, respectively is calculated for NiMoO₄ nanomaterials synthesized at 180 and 220 °C for 24 h and calcinated at 650 °C. NiMoO₄ nanomaterials and their composites find an application as electrode materials in supercapacitor.