Mo/MgO as an efficient catalyst for methane decomposition into COx-free hydrogen and multi-walled carbon nanotubes

The development of high-efficient, low-cost, and eco-friendly catalysts for the conversion of methane into COx-free hydrogen and carbon nanotubes (CNTs) remains a significant research topic. In this study, a set of inexpensive Mo/MgO catalysts with varying Mo loadings (20-50 wt%) were prepared by the conventional impregnation procedure and evaluated in this reaction. The impact of Mo content on the activity and stability as well as the nature and the yield of as-deposited carbon were investigated. The principal characterization tools such as XRD, BET, TPR, and FTIR were employed for studying the physicochemical properties of the prepared catalysts. Meanwhile, the XRD, TEM, and Raman spectra were used for the characterization of as-deposited carbon materials. The XRD and TPR results revealed that the magnesium molybdate (MgMoO4) phase was the major component in the composition of 20-40%Mo/MgO catalysts, while the 50%Mo/MgO catalyst comprised a mixture of non-interacted MoO3 species and the MgMoO4 phase. The catalytic activity results showed that the MgMoO4 phase acts as active site in the current reaction. Therefore, the 30%Mo and 40%Mo/MgO catalysts afforded superior activity and longevity in terms of H-2 yield and carbon accumulation as compared with the 50% Mo/MgO catalyst. TEM images of as-deposited carbon showed that all Mo/MgO catalysts produced multi-walled carbon nanotubes (MWCNTs) bundles with very uniform and narrow diameters. The presence of highly dispersed and stabilized Mo nanoparticles in the MgMoO4 matrix was the primary reason for the high activity, particularly stability, and growth of the MWCNTs bundles.

Automated summary

In this study, a series of Mo/MgO catalysts were prepared, and it was found that the 30%Mo and 40%Mo/MgO catalysts exhibited higher activity and stability in methane conversion reaction and produced multi-walled carbon nanotubes bundles with uniform diameters. The presence of highly dispersed and stabilized Mo nanoparticles in the MgMoO4 matrix played a primary role in achieving high activity, particularly stability, and growth of the multi-walled carbon nanotubes bundles.