Porous silica encapsulated attapulgite (ATP) clay supported nickel catalysts were prepared by successive precipitation-deposition method, which were tested in an ammonia decomposition for production of COx-free hydrogen. The textural and structure properties of Ni/ATP catalysts and silica encapsulated Ni/ATP catalysts were characterized by X-ray diffraction, scanning and transmission electron microscopy, N-2 sorption, thermogravimetry-differential thermal analysis, hydrogen temperature-programmed reduction. The results reveal that ATP supported Ni catalysts possess a suitable specific surface area and pore volume, as well as nano-structure. Ni nanoparticles are mostly located on the external surface of ATP supports. With an increase on Ni loading content from 10 to 50 wt % (theoretical value), the ammonia conversion increases gradually. Owning to porous silica enwrapping, the Ni-30/ATP@SiO2 catalysts show a higher specific activity (17.0 mol g(Ni)(-1) h(-1), 650 degrees C) and stability than Ni-30/ATP catalysts. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.