One-pot synthesis of supported Ni@Al2O3 catalysts with uniform small-sized Ni for hydrogen generation via ammonia decomposition

Nickel based materials are the most potential catalysts for COx-free hydrogen production from ammonia decomposition. However, the facile synthesis of supported Ni-based catalysts with small size Ni particles, high porosity and good structural stability is still of great demand. In this work, uniform small-sized Ni particles supported into porous alumina matrix (Ni@Al2O3) are synthesized by a simple one-pot method and used for ammonia decomposition. The Ni content is controlled from 5 at.% to 25 at.%. Especailly, the 25Ni@Al2O3 catalyst shows the best catalytic performance. With a GHSV of 24,000 cm(3) g(cat)(-1) h(-1), 93.9% NH3 conversion is achieved at 600 degrees C and nearly full conversion of NH3 is realized at 650 degrees C. The hydrogen formation rate of 25NiAl catalyst reaches 3.6 mmol g(cat)(-1)min(-1) at 400 degrees C and 7.8 mmol g(cat)(-1)min(-1) at 450 degrees C. The enhanced activity observed on 25Ni@Al(2)O(3 )catalyst can be attributed to the structural characteristic that large amounts of uniform-sized small (7.2 +/- 0.9 nm) Ni particles are highly dispersed into porous alumina matrix. The aggregation of active metallic Ni particles during the high temperature reaction can be effectively prevented by the porous alumina matrix due to the strong interaction between them, thus ensuring a good catalytic performance. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Nickel based catalysts supported on porous alumina matrix with small size Ni particles exhibit excellent catalytic performance for ammonia decomposition, achieving high ammonia conversion rates and hydrogen formation rates. The structural characteristics of uniform-sized small Ni particles highly dispersed into the porous alumina matrix contribute to the enhanced catalytic activity.