Inhibited hydrogen poisoning for enhanced activity of promoters-Ru/Sr2Ta2O7 nanowires for ammonia synthesis

In this work, strontium tantalate (Sr2Ta2O7) nanowires were used for the first time as a support of ruthenium catalysts for ammonia synthesis. The highest ammonia synthesis activity of 1582 μmol g-1cat h-1 was observed with Ru/Sr2Ta2O7 catalysts prepared with molar ratio of Sr(OH)2/Ta2O5 at 4. After loading promoters, the ammonia synthesis activity was significantly improved to 4856, 5004 and 5038 μmol g-1cat h-1 for K-, Rb- and Cs- modified Ru/Sr2Ta2O7 catalysts. Characterization and kinetic experiments indicate that the improved ammonia synthesis rate of promoters-Ru/Sr2Ta2O7 catalysts was attributable to the combined effect of alleviated hydrogen poisoning through the promotion of hydrogen spillover from Ru species to support of Sr2Ta2O7 and enhanced activation of N2 due to increased electron density of Ru sites because of electron donation from introduced oxygen vacancies and promoters. The study not only clarifies the role of promoters in ammonia synthesis, but also provides an excellent Ru catalyst on Sr2Ta2O7 nanowires for ammonia synthesis.