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/Al 2 O 3 , 40 wt% Ni/Al 2 O 3 , 15 wt% Ni-Co (9:1)/MgO, and 50 wt% Ni/MgO, in CMD experiments performed in a quartz reactor. The 40 wt% Ni/Al 2 O 3 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 H 2 production, attributed to the synergistic effect of active metals, Ni and Co. After purification, the carbon content of the tested 40 wt% Ni/Al 2 O 3 , 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. • Simultaneous production of MWCNTs and high-purity H 2 was achieved via CMD using Ni-based catalysts. • 40 wt% Ni/Al 2 O 3 showed the highest carbon yield (90%), highlighting the impact of Ni loading and morphology. • 15 wt% Ni-Co/MgO demonstrated the most stable H 2 production due to the synergistic effect of Ni and Co, achieving a low activation energy of 42.9 kJ mol −1 . • The MgO supported catalysts enabled easy purification and metal recovery, reducing cost and environmental impact. • Produced MWCNTs with >95% purity met commercial industry quality standards.