Deciphering the influence of support in the performance of NiFe₂O₄ catalyst for the production of hydrogen fuel and nanocarbon by methane decomposition

Wet chemical synthesis route was used to synthesis nickel ferrite (NiFe₂O₄) nanoparticle. Later on the synthesized NiFe₂O₄ were supported on the surface of three traditional supports such as Al₂O_3, MgO and TiO₂ to get NiFe₂O₄/Al₂O₃, NiFe₂O₄/TiO₂ and NiFe₂O₄/MgO catalysts. The activity profile of each catalyst was evaluated in a fixed-bed reactor for direct methane decomposition at 800 °C. For both fresh and spent catalysts, many characterization techniques have been employed mainly XRD, FESEM, HRTEM, Raman spectroscopy, TGA, and nitrogen adsorption-desorption isotherm. X-ray powder diffraction studies revealed that all synthesized catalysts have a cubic spinel crystal structure. The XRD confirm the presence of NiFe₂O₄ particles in the component of fresh NiFe₂O₄/MgO, NiFe₂O₄/TiO₂ and NiFe₂O₄/Al₂O₃ catalysts. Temperature Program Reduction (TPR) unveiled the presence of Ni oxides and Fe oxides by displaying reduction peaks in their respective temperature regions. The N₂ adsorption-desorption isotherms of the fresh all catalysts reveal that these catalysts have a mesoporous structure. Activity data concluded NiFe₂O₄/MgO to be the most active catalysts among the tested catalysts methane conversion magnitude of 41.13 % and H₂ formation rate of 84.40 × 10⁻⁵ mol H₂ g⁻¹ min⁻¹. On the other hand, the H₂ formation rate drastically declined and very poor activity of both NiFe₂O₄/TiO₂ and NiFe₂O₄/Al₂O₃ catalysts was observed in the current work. XRD patterns, FESEM images and TGA analysis of spent NiFe₂O₄/MgO catalyst shown the filamentous carbon formation which secondarily confirm its higher activity, while its absence in catalysts of NiFe₂O₄/TiO₂ and NiFe₂O₄/Al₂O₃. TGA analysis of the carbon deposited on the NiFe₂O₄/MgO catalyst showed that the amount of carbon was approximately 64 wt%. It was suggested that the formation of nickel-iron carbide revealed by XRD studies of spent catalysts may be the factor related to their poor activity while discussing the structure-activity relationship. Likewise, the higher degree of dispersion related to NiFe₂O₄/MgO as displayed by XRD, FESEM and TPR investigations, played a vital role in accelerating the rate of hydrogen formation.