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

• Published in: International journal of hydrogen energy Vol. 46; no. 5; pp. 4045 - 4054
• Main Authors: Gu, Yingqiu, Ma, Yinglan, Long, Zhouyang, Zhao, Shuang, Wang, Ying, Zhang, Weichao
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 19.01.2021
• Subjects: Ammonia decomposition; COx-free hydrogen; Supported Ni catalyst; Uniform small-sized; Uniform small-sized; Supported Ni catalyst; Ammonia decomposition; COx-free hydrogen
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2020.11.003

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 cm3gcat−1h−1, 93.9% NH3 conversion is achieved at 600 °C and nearly full conversion of NH3 is realized at 650 °C. The hydrogen formation rate of 25NiAl catalyst reaches 3.6 mmol gcat−1min−1 at 400 °C and 7.8 mmol gcat−1min−1 at 450 °C. The enhanced activity observed on 25Ni@Al2O3 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. Uniform small-sized Ni particles supported into porous alumina matrix (Ni@Al2O3) are synthesized by a simple one-pot method and used to effectively catalyzing ammonia decomposition for the production of COx-free hydrogen. [Display omitted] •Supported Ni@Al2O3 catalysts are synthesized by a simple one-pot method.•25Ni@Al2O3 catalyst shows optimal catalytic NH3 decomposition performance.•The good catalytic performance is attributed to the structural characteristics.•Aggregation of Ni particles can be prevented by alumina due to the interaction.