Low Apparent Activation Energy of Ammonia Synthesis over Ru Catalyst Supported by Hydrogen Storage Material

Ruthenium is an excellent catalyst for ammonia synthesis and recently shows quite high activity when supported on materials with high electron-donating and hydrogen-absorbing properties. The high activity is generally considered to originate from the two effects: the electron-donating property of the support, which reduces its apparent activation energy (^appE_a) to half of pure Ru’s ^appE_a, and the hydrogen-absorbing property, which increases the active site by suppressing hydrogen poisoning, a drawback of ruthenium catalysts. Here, we investigated the catalytic performance of ruthenium loaded on TiMn₂, a hydrogen storage material without electron-donating property to ruthenium. Ruthenium on TiMn₂ showed the ^appE_a reduced by half despite the lack of electron-donating property. It is plausible that the decreased ^appE_a is due to the elimination of hydrogen over Ru by TiMn₂. The hydrogen storage capacity is also an essential factor in discussing the ^appE_a.