The Ba modified ZrO2 materials were prepared and loaded Ru nanoparticles for ammonia decomposition to COx-free hydrogen reaction. The catalytic activity of Ru supported on Ba-ZrO2 derived from sol-gel process (Ru/Ba-ZrO2) is found to be several times of those for Ru/ZrO2 without any promoter and Ru-Ba/ZrO2 catalysts prepared by conventional immersion method at the identical conditions. It is found that the formation of BaZrO3 phase in Ba-ZrO2 can enhance the electron-donating ability of the support and Ru nanoparticles dispersion. Therefore, mobile electrons would be transferred from BaZrO3 to the surface Ru particles, facilitating the recombinative desorption of N over Ru particles, leading to the increase of activity for ammonia decomposition sufficiently. Additionally, the suitable size of spherical Ru particles with average size of 2.4 nm for the formation of active sites are also responsible factors for the higher activity of this catalyst. The catalytic performance of Ru/Ba-ZrO2 catalyst can also be further improved by introducing of K and Cs promoters, and the apparent activation energies over Ru/Ba-ZrO2 of 94.1 kJ/mol decrease to 70.7 kJ/ mol and 64.2 kJ/mol for K and Cs promoted Ru/Ba-ZrO2, respectively. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.