Transformation of atomically dispersed reduced graphene aerogel (rGA)-supported complexes, Ir^I(C₂H₄)₂⁺, with an iridium loading of 9.9 wt%, to form low-nuclearity clusters was investigated during ethylene hydrogenation catalysis. Continuous-scan X-ray absorption spectra demonstrate the formation of clusters well approximated as Ir₄ during reaction at 100 °C in flowing equimolar ethylene and H₂. The Ir₄ clusters transformed into clusters well approximated as Ir₆ when the feed molar ratio was switched to H₂:C₂H₄ = 2 and remained stable in pure H₂ at 100 °C. Catalyst performance data show that hydrogenation activity increased with metal nuclearity in the order of atomically dispersed iridium/rGA≪ Ir₄/rGA < Ir₆/rGA. Continuous scan X-ray absorption data, complemented with aberration-corrected scanning transmission electron microscopy images, demonstrate that the supported clusters approximated as Ir₆ are stable even in H₂ at atmospheric pressure and 100 °C. These supported iridium clusters are among the ones having the highest metal loadings reported for a supported metal cluster catalyst.

研究了在乙烯加氢催化过程中原子分散的还原石墨烯气凝胶 (rGA) 负载的配合物 Ir ^I (C ₂ H ₄ ) ₂ ⁺的转化，铱负载量为 9.9 wt%，以形成低核团簇。连续扫描 X 射线吸收光谱表明，在 100 °C 下，在流动的等摩尔乙烯和 H _{2的反应过程中，簇的形成非常接近于 Ir 4}。当进料摩尔比切换为 H ₂ :C ₂ H ₄时，Ir ₄簇转变为非常近似于 Ir _6的簇= 2 并在 100 °C 下 在纯 H _{2中保持稳定。}催化剂性能数据表明，加氢活性随着金属核的增加而增加，其顺序为原子分散的铱/rGA≪ Ir ₄ /rGA < Ir ₆ /rGA。连续扫描 X 射线吸收数据，辅以像差校正的扫描透射电子显微镜图像，表明近似为 Ir ₆的受支持簇即使在大气压和 100 °C的 H _{2中也是稳定的。}这些负载型铱簇属于负载型金属簇催化剂所报道的具有最高金属负载量的那些。