Yeh Chen-Hao, Lin Yu-Chieh, Ho Jia-Jen
Department of Chemistry, National Taiwan Normal University, No. 88, Section 4, Tingchow Road, Taipei 116, Taiwan.
Phys Chem Chem Phys. 2014 Apr 28;16(16):7394-400. doi: 10.1039/c3cp55144j.
The N2 bond cleavage is the rate-limiting step in the synthesis of ammonia, and ruthenium is a catalyst well known for this reaction. The double-icosahedral (D5h) Ru19 cluster is famous as an active catalyst, and has a remarkable stability towards the adsorption of H2, N2 and CO. Using first-principles calculations, we have investigated the adsorption and dissociation of dinitrogen on a double-icosahedral Ru19 cluster. Our results show that the hollow site in the rhombus region (BHB site) of the Ru19 cluster possesses the greatest catalytic activity to dissociate N2, with the reaction barrier of 0.89 eV and an exothermicity of -1.45 eV. Multiple coadsorption of N2 on the cluster (i.e. coadsorption of 2N2 and 3N2 on a single Ru19 cluster) causes the barrier to dissociate N2 to be less on a BHB site than for adsorption of a single N2. To understand the catalytic properties of a Ru19 cluster towards N2 bond cleavage, we calculated the electron population, vibrational wavenumbers and local densities of states; the results are explicable.
N₂键的断裂是合成氨过程中的限速步骤，而钌是该反应中一种广为人知的催化剂。双二十面体（D5h）Ru₁₉团簇作为一种活性催化剂而闻名，并且对H₂、N₂和CO的吸附具有显著的稳定性。我们利用第一性原理计算方法，研究了双二十面体Ru₁₉团簇上氮气的吸附和解离过程。我们的结果表明，Ru₁₉团簇菱形区域的中空位点（BHB位点）对N₂解离具有最大的催化活性，反应势垒为0.89 eV，放热为 -1.45 eV。团簇上N₂的多重共吸附（即单个Ru₁₉团簇上2N₂和3N₂的共吸附）使得BHB位点上N₂解离的势垒低于单个N₂的吸附势垒。为了理解Ru₁₉团簇对N₂键断裂的催化性质，我们计算了电子布居、振动波数和局域态密度；结果是可以解释的。
