Stoichiometric-Ratio-Controlled Fe and Ni Non-Noble Metal Catalysts Supported on γ-Al2O3 for Turquoise Hydrogen and Carbon Nanotubes Production.

Herein, we synthesized a series of catalysts comprising iron (Fe), and nickel (Ni) supported on γ-Al₂O₃ nano-powder (Fe-Ni/γ-Al₂O₃) by controlling the stoichiometric ratio of the metals through the facile co-precipitation method. The ratio of Fe and Ni on the γ-Al₂O₃ support varied from 0 to 70 weight percent (wt %). The freshly prepared catalysts phase, structure, and crystallinity exhibited variability as the Fe and Ni stoichiometric ratios were altered. The catalyst demonstrated effective performance in methane cracking, producing turquoise hydrogen and carbon nanotubes (CNTs) using a temperature-programmed reactor coupled with mass spectrometry. It was observed that the Fe3Ni4 catalyst, comprising 30 % Fe and 40 % Ni, exhibited a maximum methane conversion rate of 85 % and a hydrogen yield of 72.55 %. Moreover, the values of turnover frequency (2.38 min^-1) indicated that the Fe3Ni4 had a better production rate and was consistent with the conversion process throughout the reaction. The structural attributes of the spent catalysts were examined, revealing variations in the lateral length, uniformity, and diameters (~33 to 56 nm) of the produced Carbon Nanotubes (CNTs) when transitioning from catalyst Fe0Ni7 to Fe7Ni0. The investigation underscored the significance of metal stoichiometrically controlled catalysts and their catalytic efficacy in methane cracking applications.