Synergetic effects of Al addition on the performance of CoFe₂O₄ catalyst for hydrogen production and filamentous carbon formation from direct cracking of methane

Improving methane catalytic decomposition process was deemed an effective approach for hydrogen production. Here, a novel catalyst Al_xCo_1-xFe₂O₄ with a variable aluminum content was synthesized via a co-precipitation route for the direct cracking of methane. The catalytic activity of Al_xCo_1-xFe₂O₄ was performed in a fixed bed reactor at temperature of 800^°C and 20 mL/min of fed gas. A sequence of characterizations, including SEM, BET, XRD, XPS, Raman and TGA for fresh and spent catalysts, was exploited to examine the influence of Al_x content on the morphology, porosity, structure, chemical composition, and cation distribution of Al_xCo_1-xFe₂O_4. As the Al_x content increased in Al_xCo_1-xFe₂O₄ their morphology became more fractal and decreased in particle size, lattice parameter, lattice size, while their pore surface increased. Further cation re-distributions from octahedral to tetrahedral sites as Fe³⁺ and Al³⁺ relocated in the Tetrahedral site and Oxygen lattice decreased as observed from Raman and XPS results. Catalytic activity studies showed that Al_x content of 0.6 in Al_xCo_1-xFe₂O₄ lead maximum methane conversion up to ∼ 91.10 % and hydrogen formation rate of 1.780 ×10^-3 mol H₂ g^-1 s^-1. The catalytic activity behavior was explained in correlation with the characteristics of spent catalysts.