A mechanistic insight into rhodium-doped gold clusters as a better hydrogenation catalyst

The reaction mechanism of the hydrogenation of ethylene on pristine (Au_n, n = 8 and 20) and rhodium-doped (Au_nRh) gold clusters was unveiled by theoretical calculations. All reaction pathways are predicted and the thermodynamic and kinetic parameters are computed and compared. Doping a rhodium atom on the magic gold cluster surface is effective in reducing the activation barriers for hydrogenation and in creating two competitive pathways with significantly higher turnover frequencies. The lower barriers of hydrogenation on the Au_nRh clusters were analyzed and explained based on distortion/interaction activation strain (DIAS) analysis. Further insights into the reaction mechanism on both types of clusters are provided by intrinsic bond orbital (IBO) calculations. This theoretical study provides an idea to elucidate the hydrogenation mechanism on Au clusters and the effect of the rhodium dopant on the catalytic process.