A wet impregnation method is used to synthesize Ni nanocatalysts supported on naturally abundant mica nanosheets for decomposition of ammonia to COx-free hydrogen. The prepared catalysts are characterized by XRD, SEM, TEM, N-2 sorption, TG, XPS, H-2-TPR and NH3/H-2-TPD techniques. The catalytic tests exhibit that the Ni/mica catalysts are highly active for ammonia decomposition. The two-dimensional structure of mica favors mass transportation, which can remarkably promote the catalytic process. The NH3/H-2-TPD curves of Ni/mica show no desorption signals of NH3 and H-2, indicating the presence of weak desorption energy barrier. The content of Ni in the catalysts is related to the crystallite size of Ni species, affecting their catalytic properties. As demonstrated in this study, the Ni/mica catalyst with 15% Ni loading amount exhibits the highest catalytic activity and long-term stability. At a high space velocity of 30000 cm(3) g(cat)(-1)h(-1), 97.2% ammonia conversion is achieved over the 15%Ni/mica catalyst at 650 degrees C, indicating the Ni/mica is a promising catalyst for ammonia decomposition. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.