Optimization of Ruthenium Particle Size and Ceria Support for Enhanced Activity of Ru/CeO2 Cluster Catalysts in Ammonia Synthesis Under Mild Conditions

To meet the increasing demand for small-scale NH3 production, catalysts that work under milder conditions than those of the Haber-Bosch process are essential. In this study, Ru clusters and nanoparticles were impregnated on five different CeO2 supports to prepare Ru/CeO2 catalysts for NH3 synthesis at 400 degrees C and 0.1 MPa. The basicity of the CeO2 support and Ru particle size significantly influenced the catalytic activity. The catalytic activity increased with decreasing Ru particle size, reaching the maximum of similar to 200 mmol g(Ru) (-1) h(-1) at similar to 1 nm, which is ascribed to a high proportion of unique active sites different from the B-5-type sites. Our findings demonstrate that Ru cluster catalysts are advantageous over Ru nanoparticle catalysts for NH3 synthesis. [GRAPHICS] .