Influence of Zn and Ni dopants on the physicochemical and activity patterns of CoFe₂O₄ derived catalysts for hydrogen production by catalytic cracking of methane

Zinc and nickel incorporated CoFe₂O₄ materials have been synthesized via a wet chemical method. Characterization of these cobalt ferrite based catalysts was undertaken using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and thermal gravimetric analysis (TGA). The catalytic activity of these materials was evaluated by monitoring the direct cracking of methane for the production of hydrogen and carbon. The XRD and SEM results indicated that Ni incorporation preserves the inverse spinel structure of CoFe₂O₄, whilst Zn incorporation changes its microstructure. The Co 2p, Fe 2p and O 1 s XP spectra confirm the expected oxidation states of the elements in the near surface region of the catalysts. Raman spectra indicate cation redistribution between tetrahedral and octahedral sites upon Ni and Zn incorporation into CoFe₂O₄. BET surface area analysis revealed Ni incorporation is more effective in increasing the surface area of CoFe₂O₄ compared to Zn incorporation. Indeed, catalytic activity evaluation showed that Ni incorporation into CoFe₂O₄ improved methane conversion and correspondingly the hydrogen formation rate. In contrast, Zn incorporation led to very low catalytic activity. The spent catalysts were further characterized and the results are strongly correlated with catalytic activity.