Theoretical Investigation On Some Single Atom Catalysts And Cluster System

Many efforts and studies have been devoted to design more efficient catalysts towards energy and environment.The single atom satalysts?SACs?have the higher efficiency than the typical noble metals.Thus,it is necessary to design SACs to improve the activity and reduce the cost.The current study is mainly focused on the design of SACs about h-BN towards CO oxidation,as well as the prediction for the clusters,based on the DFT method.The details are shown below:1.The mechanisms of CO oxidation to CO₂ over single Pd and Ag atoms doped h-BN?Pd1-BN and Ag₁-BN?are systematically studied by DFT-D calculations.The results show that single Pd and Ag can be anchored on defective h-BN with boron vacancy?VB/BN?,according to the adsorption energy and diffusion barrier for them over VB/BN.The traditional Eley-Rideal?ER?,Langmuir-Hinshelwood?LH?and a termolecular Eley–Rideal?TER?of CO oxidation are simulated.Because of the lower reaction barriers,it is concluded that both the traditional LH and the new TER mechanism for CO oxidation are possible to occur at a low temperature.Due to the "CO-Promoted O₂ Activation",the TER mechanism with the lowest reaction barrier is the most relevant one for CO oxidation.More importantly,the first principles molecular dynamics?MD?simulations confirm that CO oxidation via the TER mechanism may easily occur at room temperature.The current study will shed light on principles for the design of more efficient catalysts based on the SAC concept.2.For the theoretical study,the prediction for the global minimum of clusters is a challenging task because it has to locate the global minimum of the potential energy surfaces,on which the number of local minimum increases exponentially with increasing cluster sizes.Accordingly,we performed extensive searches on the global minimum of Pt_mPd_n?m + n = 5?and PtPdSin?n = 1-7?clusters by applying the recently developed crystal structure analysis by particle swarm optimization?CALYPSO?algorithm with DFT calculations.For the Pt-Pd culsters,the results show that introducing the Pd element can modify the morphology and composition of the pure Pt5 cluster,i.e.,from a 2D planar to a 3D structure.The catalytic property for O₂ dissociation of the pure Pt5 cluster can be further improved by introducing the Pd atoms.Moreover,the Pt4Pd1 cluster with the high Pt composition and the structure of square pyramid shows the highest catalytic activity.For the Si based culsters,the chirality has been found for the lowest-energy structures of the neutral and charged PtPdSi4,neutral and anionic PtPdSi5,and cationic PtPdSi7 clusters.The first principles MD simulations show that the fluxional transformation between the chiral configurations for neutral PtPdSi4 cluster can take place at 400 K.This transformation barrier is only 0.09 eV.The current study here will help to understand the prediction of the global minimum structures of clusters by CALYPSO and design the less expensive and more efficient alloyed clusters.Moreover,this also provides one way to understand the chirality and fluxional transformation of clusters.