Catalytic methane decomposition to hydrogen and carbon over hydrotalcite-derivative composition-uniform and sintering-resistant Ni-Fe/Al2O3 alloy catalysts

Ni-Fe/Al2O3 alloy catalysts obtained from Ni3-xFexAl (x = 0-1.2) hydrotalcite-like compounds are tested in CH4 decomposition at 600 degrees C to produce H-2 and carbon. By calcination at 500 degrees C, nickel-iron-aluminum hydrotalcite is decomposed into Ni(Fe,Al)O solid solution; upon reduction at 800 degrees C, Ni-Fe alloy with uniform composition and the average size of 9.4 to 10.3 nm is formed. The Ni-Fe/Al2O3 alloy catalysts exhibit higher catalytic life and carbon yield than the Ni3Al counterpart, with the optimal alloy composition being Ni: Fe = 4:1. Carbon nanotubes are produced on all catalysts, and the average carbon diameter is decreased to a certain degree by Ni-Fe alloying. XRD indicates that Ni-Fe alloy is less sintered than Ni metal under the reaction atmosphere, which may account for the decrease in the carbon diameter. This study provides a way for the preparation of a uniform Ni-Fe alloy catalyst and its sintering resistance is helpful for controlling the carbon morphology.