Non-supported bimetallic catalysts of Fe and Co for methane decomposition into H₂ and a mixture of graphene nanosheets and carbon nanotubes

Herein, non-supported pure and mixed cobalt and iron oxide catalysts were synthesized from nitrate precursors using a simple, environmentally friendly preparation method in which water was the sole solvent. The prepared catalysts were then used to decompose methane into hydrogen and carbon (graphene nanosheets and carbon nanotubes). The fresh and spent catalysts were characterized by employing X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy-energy dispersive X-ray analysis (SEM/EDX), transmission electron microscopy (TEM) and N2 adsorption-desorption techniques. In addition, the spent catalysts were subjected to thermo-gravimetric analysis (TGA) in order to measure the quantity of carbon deposits on the spent catalysts. The results indicated that the carbon deposited over these catalysts is a mixture of graphene nanosheets and carbon nanotubes (CNT). The results indicated that the mixed oxide catalysts exhibit higher catalytic activity than the pure oxides and that Fe: Co atomic ratio represents the key factor in the catalytic activity of these mixed oxides. After 420 min under the reaction feed, the 50Fe + 50Co catalyst shows the highest catalytic activity towards methane conversion of about 52.6% compared to 41.6% and 31.8% for 75Fe + 25Co and 25Fe + 75Co catalysts, respectively.