Multiple phase α-NiMoO4 and Fe0·2Ni0·8MoO4 nanoparticles: Synthesis, characterization, and application in methanol electro-oxidation

The synthesis and crystal structure of α-NiMoO₄, and Fe_0·2Ni_0·8MoO₄ have been investigated as favorable heterogeneous catalysts for methanol electro-oxidation. The catalysts were synthesized using sol-gel-hydrothermal technology with polyvinyl alcohol as a surfactant. Characterization techniques including X-ray diffraction (XRD), ATR-FT-IR spectroscopy, field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), Brunauer–Emmett–Teller (BET) analysis, and thermo-kinetic analysis via TGA were employed. XRD results confirmed the pure monoclinic crystal structure of α-NiMoO₄. ATR-FT-IR spectra revealed distinctive bands characteristic of distorted MoO₆ octahedral units at 950 and 927 cm⁻¹, confirming α-NiMoO₄ formation. FESEM images displayed foamy-like particle morphologies. Fe_0.2Ni_0.8MoO₄ exhibited higher textural properties with a larger surface area (163.1 m²/g) and pore volume (0.250 cm³/g) compared to α-NiMoO₄ (70.01 m²/g, 0.113 cm³/g). XPS analysis of Fe_0·2Ni_0·8MoO₄ showed increased oxygen vacancies and the coexistence of Mo⁶⁺ and Mo⁵⁺states, which enhance its electronic structure and redox properties, indicating improved catalytic potential. Thermal and kinetic studies revealed significant relationships among activation energy (E_a), residual organic components, octahedral site coordination, and activation free energy (ΔG∗). The impact of citrate/PVA moiety elimination on methanol electro-oxidation rates was also analyzed. Cyclic voltammetry, linear sweep voltammetry, and chronoamperometry tests demonstrated that the Fe_0·2Ni_0·8MoO₄ electrode achieved a higher current density than the α-NiMoO₄ electrode, underscoring its enhanced catalytic performance.