Abstract
The development of efficient and stable Ru catalysts is crucial for synthesis of decarbonized NH3. Herein, a series of γ-Al2O3-supported Cs-promoted Ru catalysts were prepared, among which a 1.5CS-RU/γ-Al2O3 catalyst with a Cs/Ru molar ratio of 1.5 and a Ru size of ～2 nm exhibited high NH3 synthesis rates (6.9-30 mmol g_(cat)~(-1) h~(-1)) at ～400 °C and 1 MPa. We unraveled that the surface acidity/basicity could be changed, and new active sites could be generated at the interfaces between the Ru particles and the CsOH-Cs~0 species by tuning the Cs/Ru molar ratio. Among the active sites, Cs° (minor), which transferred electrons to Ru, was present at the boundaries of the Ru particles and CsOH (major), which attracted the dissociative hydrogen atoms from the metallic Ru surfaces via a spillover effect and changed the surface acidity/basicity. This facilitated the adsorption/desorption of reactant species, tnus promoting NH3 synthesis.
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