Abstract The influence of preparation conditions ( e.g. H 2-N 2 ratios, final nitriding temperatures) on the performance of MoN x /SBA-15 catalysts for ammonia decomposition was investigated. The variation of catalytic activity with H 2-N 2 ratios may be attributed to the variation of surface compositions and particle sizes of the active components. The variation of nitriding temperatures leads to the formation of molybdenum nitride domains of varying compositions, which are responsible for the difference in their catalytic performance with respect to ammonia decomposition. At 923 K, ammonia could be completely decomposed using 15800 ml/h·g cat of GHSV NH 3 , which shows high performance for the catalytic decomposition of ammonia.