Development of porous nickel catalysts by low-temperature Ni–Al chemical alloying and post selective Al leaching, and their application for ammonia decomposition

Micron-sized Ni–Al alloy powders (Ni–x wt.%Al, x = 40, 50, 60) were synthesized using the low-temperature chemical alloying (LTCA) at 500 °C. The three different as-prepared Ni–Al alloy powders were composed of Ni₂Al₃ and/or NiAl₃ phases while achieving thermodynamic equilibrium compositions (Ni–40 wt%Al, Ni₂Al₃; Ni–50 wt%Al, the coexistence of Ni₂Al₃ and NiAl₃; Ni–60 wt%Al, NiAl₃). The LTCA method demonstrates that it is capable of producing Al-rich Ni–Al alloy powders while maintaining a particle size similar to that of the starting Ni particles. The three Ni–Al alloy powders were used as precursor materials to fabricate porous nickel catalysts through a selective aluminum leaching process, followed by the enlargement of the surface area. Alteration of the material characteristics with respect to the leaching time was investigated using XRD, FESEM-EDS, TEM, XPS, TPR, BET, and particle size analysis. The nickel skeletal catalysts with the increased BET-surface areas (50–111 m²/g) displayed high reactivity toward ammonia decomposition.