Revealing hydrogen migration effect on ammonia synthesis activity over ceria-supported Ru catalysts

Catalytic reactions involving hydrogen over reducible oxide-supported metal catalysts are inseparable from the hydrogen storage capacity and hydrogen migration, which are mainly dependent on the interaction between reducible oxides and active metals. In this work, we report that the hydrogen migration rate of Ru/CeO 2 could be tuned by changing cerium nitrate solvents for the preparation of ceria . There are more kinds of oxygen species and a large amount of Ce 3+ concentration, defects and Ru−O−Ce interfacial sites for Ru catalyst supported on ceria obtained by ethanol-precipitated synthesis, resulting in a reduction in the amount of the exposed Ru species and proportion of Ru metal. In such a case, the migration and desorption of hydrogen species as well as nitrogen activation would be inhibited. Conversely, there are a higher ratio of Ru metal and a great deal of the Ru exposure for Ru catalyst supported on ceria obtained by water-precipitated synthesis, facilitating the migration and desorption of hydrogen species, as well as nitrogen activation. As a result, the water-precipitated synthesized ceria-supported Ru catalyst has 4.9-fold higher in catalytic activity than Ru catalyst supported on the ethanol-precipitated synthesized ceria. This work provides insight into the design of Ru catalysts used ammonia synthesis by controlling hydrogen spillover and migration between Ru species and CeO 2 . • Two ceria prepared by hydrothermal synthesis and ethanol-thermal synthesis are used as support of Ru catalysts. • Preparation method changes the metal-support interactions and mobility of hydrogen species for catalysts. • Hydrothermally synthesized ceria-supported Ru catalyst shows excellent ammonia synthesis performance.