Three kinds of Ce0.8Zr0.2O2 solid solutions synthesized via surfactant-assisted route, co-precipitation, and sol-gel method were used as supports of Ni-based catalysts by impregnation. Their catalytic activities in ammonia decomposition to hydrogen were tested, and the structural effect of support and the influence of nickel content on catalytic activity were evaluated. Mesoporous/high-surface-area Ce0.8Zr0.2O2 support synthesized by surfactant-assisted method exhibited better promoting effect than other supports when the same content of Ni was loaded. The interactions between Ni species and Ce0.8Zr0.2O2 supports were found to greatly affect the chemical properties of catalysts, including redox, H-2 adsorption, and catalysis. The promoting effects of Ce in catalysts, plentiful vacancies in the solid solutions due to the doping of Zr4+, and high surface areas of the supports were discussed on the ammonia decomposition activities of the resultant catalysts, as well as the influence of hydrogen spillover. The ammonia conversion of 95.7% with the H-2 producing rate of 89.3 mL/min.g(cat), was achieved at 550 degrees C over the Ni catalysts supported on the mesoporous/high-surface-area Ce0.8Zr0.2O2. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.