Boosting turquoise hydrogen and carbon nanotube production via catalytic methane decomposition: influence of active metal ratios in Fe5–Co–Zn/γ-Al2O3 nanocatalysts

Abstract

The present study reports the synthesis of a series of nanocatalysts (NCs) comprising iron (Fe), cobalt (Co), and zinc (Zn) supported on γ-Al₂O₃ nanopowder (Fe5–Co–Zn/γ-Al₂O₃) by tuning the metals stoichiometric ratio using a facile co-precipitation approach. The powder X-ray diffraction patterns and Raman spectra revealed that the freshly synthesized Fe5–Co–Zn/γ-Al₂O₃ is composed of hexagonal Fe₂O₃, cubic Co₃O₄, and hexagonal ZnO phases. The NCs exhibited efficient performance in CH₄ decomposition, yielding turquoise hydrogen (H₂) and carbon nanotubes (CNTs) as solid carbon by-products. The active metals consisted of 50% Fe, 5% Co, and 15% Zn as Fe5Co0.5Zn1.5 given a maximum CH₄ conversion of 90% and an H₂ yield of 92.2%, which are considerably higher than those of many other previously reported NCs. The structural characteristics of the spent NCs (S-Fe5Co2Zn0 to S-Fe5Co0Zn2) were examined, showing variation in the growth and quality of CNT. Moreover, the electron microscopy micrographs suggested that the CNTs growth plausibly followed the base-growth model. The CNTs are also effectively isolated from spent NCs. This study paves the way for a streamlined approach to designing and unravelling the intricate distribution of active metals on suitable supports, offering deeper insights into optimizing CH₄ decomposition into H₂ and high-quality CNTs.