Theoretical Design Of Transition Metal Catalyst Based On First Principle Methods

The development of transition metal catalysts with high performance is a significant issue in many chemical industry fields.The trial-and-error approaches are still a common practice to search for highly efficient catalysts in the laboratory,largely due to the lack of deep insight into the fundamental relationship between structure feature of reactions site and its catalytic performance.To achieve a rational design of optimal transition metal catalysts,it is important to propose a universal design principle to guide the search.In this thesis,after investigating the electron structure and reaction reactivity of transition metal catalysts by density functional theory calculations on some classical thermocatalytic and electrocatalytic reactions,we identify the characteristics of the active site and construct a structure-reactivity relationship based on our proposed structure descriptors,by which transition metal catalysts with high performance can be rationally designed.1、We study Pd-based nanocluster for direct synthesis of H2O2 by density functional theory(DFT)calculations.It’s found that average valence electron of Pd-shell atoms can be tuned by the difference of electronegativity between Pd and doped element,which accordingly adjusts activity and selectivity of the Pd-based nanocatalysts.The ratio of electronegativity between Pd and doped element is identified as structure descriptor,and is used to screen out transition metal element as dopant.At last,promising Pd-based nanocluster with the catalytic selectivity exceeding the state-of-the-art experimental catalyst are predicted.2、We study the ORR/OER/HER activities of functional graphene supported transition metal single atom catalysts.We construct a structure descriptor based on the local environment of the catalytic center,including electron occupation number on d-orbital,the coordination number and the electronegativity of the transition metal atom and the nearest neighboring atoms,which can be correlated with the catalytic activity of single atom catalysts.The structure descriptor is used for an exhaustive search for promising single atom catalysts systems,which is validated by available experimental results.The application of structure descriptor can be extended to macrocyclic molecules supported transition metal single atom catalysts.3、Using the prototype CO oxidation as benchmarks,we have performed an exhaustive search for highly active pristine MgO and O-vacancy MgO supported transition single atom catalysts,and further derived a universal design principle to evaluate the activities of single atom catalysts by combining BEP relationship,Sabatier analysis and natural bonding orbital analysis.Results provide insights into the catalytic activity trend of single atom catalysts and the role of O-vacancy in enhancing the reactivity of single atom catalyst.It’s found that Ag/MgO and Ag/O-vacancy MgO possess superior activity to other single atom catalyst systems.4、First principle calculation is performed to study CO oxidation on Au cluster and Au single crystal surface.We propose that the geometry index of surface Au atoms,including general coordination number and curvature angle,can act as simple,empirical structure descriptors,and quantify the geometry effect of reaction site on the adsorption strength and catalytic activity.At last,a structure-adsorption-activity relationship is built to assess CO oxidation activity of Au cluster,which is used to explore the size-or morphology-dependent CO oxidation activity of Au cluster.