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 Fe0.2Ni0.8MoO4 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. Fe0.2Ni0.8MoO4 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 Fe0.2Ni0.8MoO4 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 (Ea), 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 Fe0.2Ni0.8MoO4 electrode achieved a higher current density than the α-NiMoO4 electrode, underscoring its enhanced catalytic performance.