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

The synthesis and crystal structure of α-NiMoO 4 , and Fe 0.2 Ni 0.8 MoO 4 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-NiMoO 4 . ATR-FT-IR spectra revealed distinctive bands characteristic of distorted MoO 6 octahedral units at 950 and 927 cm -1 , confirming α-NiMoO 4 formation. FESEM images displayed foamy-like particle morphologies. Fe 0.2 Ni 0.8 MoO 4 exhibited higher textural properties with a larger surface area (163.1 m 2 /g) and pore volume (0.250 cm 3 /g) compared to α-NiMoO 4 (70.01 m 2 /g, 0.113 cm 3 /g). XPS analysis of Fe 0.2 Ni 0.8 MoO 4 showed increased oxygen vacancies and the coexistence of Mo 6+ and Mo 5+ 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 0.2 Ni 0.8 MoO 4 electrode achieved a higher current density than the α-NiMoO 4 electrode, underscoring its enhanced catalytic performance. • α-NiMoO4 and Fe0.2Ni0.8MoO4 synthesized via the sol-gel method. • Fe0.2Ni0.8MoO4 demonstrated superior current density and methanol electro-oxidation rates compared to α-NiMoO4. • Oxygen vacancies and Mo6+/Mo5+ states in Fe0.2Ni0.8MoO4 significantly improved redox properties. • Identified critical links between activation energy, organic residue elimination, and catalytic performance.