Abstract
Abstract Catalysts containing Co and Al were prepared to obtain graphene and carbon nanotubes (CNTs) via the catalytic decomposition of CH4. The catalysts were prepared by co-precipitation with molar percentages of Co between 50 and 100%. The effects on the formed carbon of the catalyst composition, reaction temperatures of 500–900 °C, and activation with hydrogen were evaluated. The carbon that formed during the reactions was analyzed using Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and temperature-programmed oxidation (TPO). The Raman spectra of the samples containing Al were characteristic of CNTs, with the IG/ID ratio increasing as the Co/Al ratio and reaction temperature increased. The Co100 sample presented a Raman spectrum indicative of few-layer graphene. The TPO analysis revealed cobalt carbide oxidation for the Co100 sample, and this phase was related to the formation of graphene. CNTs were favored by Co Al mixed oxides and reaction temperatures of 500–700 °C. Graphene was favored by the Co3O4 phase and higher reaction temperatures.
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