H_2在Fe,Pt,Ni表面解离的模拟研究

采用基于密度泛函理论的分子模拟手段,以工业常用的金属催化剂Fe,Ni,Pt为代表,构建了催化剂模型,通过对H_2在不同金属表面的吸附构象、解离能垒以及电子密度分布变化情况进行考察,研究H_2在上述模型上的吸附与解离过程。结果表明,H_2在不同金属表面的物理吸附构象存在差异,可能与不同金属晶胞结构及其表面结构存在差异有关。解离能垒研究结果表明,H_2在Fe,Pt,Ni这3种过渡金属表面解离的能垒较为接近,其中在Fe(110)面解离的能垒最低。解离过程中的电子云密度分布变化表明,H_2在3种金属表面存在着相同的电荷转移趋势,推测H_2的解离是通过过渡金属的d轨道与H_2的σ~*反键轨道间的相互作用实现的。

SIMULATION STUDY ON ADSORPTION AND DISSOCIATION OF HYDROGEN ON IRON,PLATINUM AND NIKEL METALS

The adsorption and dissociation mechanism of hydrogen on Fe (1 1 0), Pt (1 1 1) and Ni (1 1 1) surfaces were built based on the density functional theory (DFT) to study different adsorption conformations, dissociation energy barrier as well as electron density changes. DFT calculations indicated that the physical adsorption conformations of H2 on different metal surfaces are different, which may be related to the differences of cell structures and surface structures of different metals. Further calculations on the three metal surfaces showed that the three transition metals have similar catalytic activity on H2 dissociation, with the lowest energy barrier of hydrogen dissociation on Fe (1 1 0). The change of electron density distribution during the dissociation process indicated that H2 has the same electric charge transfer trend on the surface of three metals. It was speculated that H2 dissociation is achieved through the interaction between the d orbital of transition metal and the orbital σ* antibonding orbital of H2.