Using density functional theory (DFT) with numerical atomic functions including dispersion corrections, we establish a series of energy changes and Gibbs free energies of in situ and ex situ substitution by ammonia on Ni-Mo-S nanocluster, which includes Ni-Mo-Edge, Ni-S-Edge and Corner-Site. The results show that the in situ substitution on all active sites on Ni-Mo-S is hard to happen. The –SH group and hydrogen atom on coordinately unsaturated sites (CUS) of Ni-S-Edge can form H₂S under a moderate condition, whereas the sulfur atoms on Ni-Mo-Edge are rather difficult to form H₂S. The ex situ substitution of sulfur atoms on both Ni-S-Edge and Ni-Mo-Edge is energetically favored; however, the substitution may only occur on Ni-S-Edge under low partial pressure of ammonia based on the steady state of Ni-Mo-S active phase. The orbital properties show the eigenvalue has increased after substitution, which indicates the decreasing of binding electron capacity. Furthermore, the HDS performance would drop remarkably attributed to steric hindrance and lacking of activated hydrogen after substitution.

我们使用密度泛函理论（DFT）结合数值原子函数（包括色散校正），建立了一系列的能量变化和吉布斯自由能，在包括Ni-Mo-Edge在内的Ni-Mo-S纳米簇上被氨原位和非原位取代，Ni-S-Edge和Corner-Site。结果表明，Ni-Mo-S上所有活性位上的原位取代都很难发生。Ni-S-Edge的配位不饱和位点（CUS）上的–SH基团和氢原子可以在中等条件下形成H ₂ S，而Ni-Mo-Edge上的硫原子则很难形成H ₂S.大力支持在Ni-S-Edge和Ni-Mo-Edge上硫原子的异位取代；然而，基于Ni-Mo-S活性相的稳定状态，取代只能在氨的低分压下在Ni-S-Edge上发生。轨道性质表明，取代后本征值增加，表明结合电子容量下降。此外，由于位阻和取代后缺乏活性氢，HDS性能将显着下降。