Preparation of Ru/ZrO2 Catalysts by NaBH4 Reduction and Their Catalytic Activity for NH3 Decomposition To Produce H2

ZrO2-supported Ru catalysts were prepared by an impregnation method and by NaBH4 reduction from RuCl3·3H2O and a commercial ZrO2 support. The catalyst prepared by NaBH4 reduction showed high activity (around 60%) at 673 K for NH3 decomposition, whereas the catalyst prepared by the impregnation method exhibited low activity (10%) under the same reaction conditions. X-ray fluorescence spectrometry indicated that the catalyst prepared by NaBH4 reduction was free of Cl, whereas the catalyst prepared by the impregnation method contained more than 5 wt % Cl from the Ru precursor. This was main factor that caused the differences in catalytic activity. In addition, the Ru/ZrO2 catalyst prepared by NaBH4 reduction was active for NH3 decomposition without H2 pretreatment, and its activity was slightly higher than that of the catalyst pretreated with H2. The transmission electron microscopy and H2 pulse chemical adsorption results demonstrated that the Ru metal particle size also affected the activity.