Hydrotalcite-derived nickel–gallium alloy catalysts with enhanced resistance against metal sintering for methane decomposition. (29th March 2023)

• Record Type: Journal Article
• Authors: Lin, Xingyi; Huang, Min; Zhu, Hong; Wan, Chunsheng; Li, Dalin; Jiang, Lilong
• Is Part Of: International journal of hydrogen energy. Volume 48:Number 27(2023)
• Page Start: 10016
• Page End: 10031
• Publication Date: 2023-03-29
• Subjects: Catalytic methane decomposition -- COx-free hydrogen -- Carbon nanotubes -- Hydrotalcite-like compounds -- Nickel–gallium alloy; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2022.12.036
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: Catalytic methane decomposition is a promising way to convert methane into CO x -free hydrogen and value-added carbon nanomaterials, but the development of a sintering-resistant catalyst is a challenge. In this study, Ni–Ga/Al2 O3 alloy catalysts with different Ga/Ni atomic ratios were prepared from Ni3− x Ga x Al ( x = 0–1.2) hydrotalcite-like compounds (HTlcs) as precursors and tested for methane decomposition. Structural and physicochemical properties of the as-prepared and used catalysts were characterized by ICP, N2 physical adsorption, XRD, H2 -TPR, H2 chemisorption, STEM-EDX, SEM, TEM, and Raman techniques. The results indicate that upon calcination at 500 °C, Ni–Ga–Al HTlcs are transferred to rock-salt Ni(Ga, Al)O oxide solid solutions, and reduction with H2 at 800 °C leads to single-phase and composition-uniform Ni–Ga alloy particles with an average crystal size of 8–10 nm. In catalytic methane decomposition at 600 °C, the alloying Ni with a suitable amount of Ga effectively enhances the catalyst life and carbon yield. Especially, Ni2.4 Ga0.6 Al shows the highest carbon yield of 61.1 g-C/g-cat, approximately 4.4 times that of the Ga-free Ni counterpart. Meanwhile, Ni–Ga alloying has a marked influence on the CNTs geometry, giving herringbone-like CNTs with small diameters and thin walls. It is gratifying to find that the Ni–Ga/Al2 O3 catalyst exhibits good resistance against sintering under the adopted reaction condition, which accounts for the formation of uniform CNTs of smaller size. The findings provide guidelines for the control of carbon morphology and geometric size in methane decomposition. Graphical abstract: Image 1 Highlights: Single-phase and composition-uniform Ni–Ga alloy is obtained from Ni–Ga–Al HTlcs. Formation of Ni(Ga, Al)O oxide solid solution is vital to yield uniform alloy particles. Alloying Ni with a suitable amount of Ga enhances the carbon yield. Ni–Ga alloy produces carbon nanotubes with small and uniform diameters. Ni–Ga alloy exhibits good resistance to sintering under the reaction condition.