The dispersed SiO2 microspheres supported Ru catalyst with enhanced activity for ammonia decomposition

Abstract Ru nanoparticles supported on SiO2 microspheres (Ru/SiO2-GUS) were prepared by the glucose-urea-metallic salt method and applied in the decomposition of ammonia. In the glucose-urea-metallic salt method, glucose as the carbon template plays a significant role in the formation of diffusion-beneficial structural properties of Ru/SiO2-GUS, and also induceds the modification of the electronic state of Ru. Ru/SiO2-GUS exhibited higher catalytic activity compared with the catalyst prepared with the impregnation method. The catalytic performance of Ru/SiO2-GUS was further enhanced with the addition of either K or Cs——the addition order and amount strongly affecting the catalytic performance. When the ratio of K/Cs to Ru is 2, the alkali metal (KOH/CsOH) solution is added in the homogeneous solution of glucose, urea, RuCl3 and the colloidal silica, the promotion effect of K/Cs is the strongest, particularly under lower reaction temperatures. However, the promotion effects of K and Cs are different as reveled by the combined results of H2-TPR, XPS and NH3-TPSR. More NH3 can be absorbed on K–Ru/SiO2-GUS and the electron density of Ru decreased. By contrast, more metallic Ru formed on Cs–Ru/SiO2-GUS, facilitating N2 recombination.