Ammonia decomposition over Ni catalysts supported on perovskite-type oxides for the on-site generation of hydrogen

Abstract

Ammonia decomposition has attracted increasing attention as a promising process for the on-site generation of hydrogen. In this study, Ni catalysts supported on perovskite-type oxides (ABO₃) were prepared and the activity for ammonia decomposition was examined. The Ni/ANbO₃ (A = Na and K) and Ni/AEMnO₃ (AE = Ca, Sr, and Ba) catalysts were less effective for this reaction. Meanwhile, the Ni/REAlO₃ (RE = La, Sm, and Gd) catalysts exhibited relatively high activity. For Ni/AETiO₃ and Ni/AEZrO₃, the performance strongly depended on the A-site element of the perovskite-type oxides, and the Sr and Ba elements were more effective than the Ca one in the respective series. The catalytic activity for Ni/AEZrO₃ was higher than Ni/AETiO₃ in the case of the same alkaline earth element, and Ni/BaZrO₃ was the most active among the samples investigated in this work. For these series, the order in the performance corresponded well with that in the basic property. The nitrogen desorption profiles revealed that the evolution of nitrogen atoms, which is one of the kinetically slow steps, effectively proceeded for Ni/SrZrO₃ and Ni/BaZrO₃ compared with the conventional Ni catalysts. This promotion effect would be ascribed to the strong basic properties of the SrZrO₃ and BaZrO₃ supports, resulting in the high activity of Ni/SrZrO₃ and Ni/BaZrO₃ for ammonia decomposition.