Porous Ni, Ni-Co, Ni-Fe, and Ni-Cu magnetic alloys with a morphology similar to a giant barrel sponge were synthesized via a facile co-precipitation procedure and then by hydrogen reduction treatment. For the first time, the non-supported alloys with their unique morphology were employed in catalytic biogas decomposition (CBD) at a reaction temperature of 700 °C and 100 mL min−1 to produce syngas and carbon bio-nanofilaments, and the catalysts’ behavior, CH4 and CO2 conversion, and the carbon produced during the reaction were investigated. All of the equimolar alloy catalysts showed good activity and stability for the catalytic biogas decomposition. The highest sustainability factor (0.66) and carbon yield (424%) were accomplished with the Ni-Co alloy without any significant inactivation for six hours, while the highest carbon efficiency of 36.43 was obtained with the Ni-Co catalyst, which is considered relatively low in comparison with industry standards, indicating a low carbon production process efficiency, possibly due to the relatively high biogas flow rate. The higher activity of the Ni-Co alloy catalyst was associated with the synergistic impact between nickel and cobalt, allowing the catalyst to maintain a high stability throughout the reaction period. Moreover, highly uniform, interwoven carbon bio-nanofilaments with a parallel and fishbone structure were achieved.

The chemical method is one of the most promising routes for the production of multi-walled carbon nanotubes. In this study, multi-walled carbon nanotubes (MWCNTs) were successfully synthesized by the modified Staudenmaier method. MWCNTs were synthesized using graphite powder at room temperature. This process does not utilize any metal catalyst. The prepared multi-walled carbon nanotubes were characterized for their crystalline, structural and thermal stability properties. The structural, crystalline and morphological characterization of The produced MWCNTs were performed by using scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction (XRD), thermogravimetric analysis(TGA), Raman analysis, and atomic force microscopy( AFM). Crystallinity and graphitization degree was observed for the produced MWCNTs have a diameter of 13.1 nm. The yield is approximately 10% of the carbon source (graphite). Moreover, the obtained MWCNTs have high thermal stability and oxidation resistance lower than 401.80 °C. The present approach provides a simple low cost and easy method of MWCNTs synthesis.