Abstract: Different carbon products were obtained by the pyrolysis of toluene using ferrocene as catalyst precursor and thiophene as promoter. The effect of catalyst and promoter on the morphologies and microstructure produced were investigated by TEM and XRD. The pyrolysis product consisted of spherical carbon nanoparticles when no catalyst or promoter was used. Some nanoparticles in the product were linked together into chain-like structures. When ferrocene was used alone, Fe-encapsulated carbon nanoparticles were the main product. When ferrocene and thiophene were used together, the product morphologies were related to the thiophene content. The above results suggest that the coexistence of Fe and S has a large synergetic effect on the pyrolysis reaction and the product formation process.