MWCNTs growth and low-carbon H₂ synthesis in the catalytic CH₄ decomposition reaction

In this study, hydrogen and MWCNTs were co-produced via the catalytic methane decomposition (CMD) using Ni-based catalysts. A comparison of catalytic activity was conducted using four catalysts: 15 wt% Ni/Al₂O₃, 40 wt% Ni/Al₂O₃, 15 wt% Ni-Co (9:1)/MgO, and 50 wt% Ni/MgO, in CMD experiments performed in a quartz reactor. The 40 wt% Ni/Al₂O₃ catalyst achieved the highest carbon yield (90%) prior to purification, whereas the 15 wt% Ni-Co (9:1)/MgO catalyst exhibited the highest and stable H₂ production, attributed to the synergistic effect of active metals, Ni and Co. After purification, the carbon content of the tested 40 wt% Ni/Al₂O₃, 50 wt% Ni/MgO, and 15 wt% Ni-Co/MgO catalysts exceeded 95%, comparable to high-purity MWCNTs reported in the literature. The MgO-supported catalyst demonstrated easier purification and metal recovery, making it a promising candidate for CMD applications. Accordingly, a kinetic study of 15 wt% Ni-Co/MgO at 575-650 °C gave an activation energy of 42.9 kJ mol⁻¹, lower than literature values, indicating enhanced catalytic efficiency.