Mo-based nanoparticles (MoO2 and Mo2C) embedded in porous carbon matrix have been synthesized by a successive hydrothermal and thermal treatment strategy. The synthesized materials were tested for COx-free H-2 production via ammonia decomposition. Various characterizations, including N-2-sorption, TGA, FTIR, TEM, XRD, EDX and XPS, were employed to investigate the morphology, component and structure of fresh and used catalysts. In terms of fresh Mo@C sample, tiny Mo-based nanoparticles (3-6 nm) are homogeneously dispersed in porous carbon matrixes, which were rapidly nitridized to MoN phases during reaction process. Most of MoN species were still embedded in carbon matrixes after 25 h stability test. For comparison, MoN@C sample was achieved via temperature-programmed ammonolysis of Mo@C sample, demonstrating the formation of MoN species and enhanced activities. The ammonia decomposition activity (similar to 90% conversion) is obtained over MoN@C catalyst at 600 degrees C and 15,000 h(-1), which is higher than that of non-pretreated Mo@C catalyst. This embedded structure also endows them with a relatively stable performance even at high temperature. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.