Study On The Dynamic Effect Of Cu₁₃ Clusters

Small clusters have attracted much attention in the field of catalysis.It is well known that the activity,selectivity and stability of catalysts are closely related to the size,shape,support and surrounding environment of the catalyst.However,the big question is:In theoretical calculation research,static structural optimization methods are usually used to study catalytic reactions with static vision.This is because the catalyst can be considered stable at the time scale at which the elementary reaction occurs.But when the size of the catalyst is reduced to a certain extent,its dynamic effect becomes more and more significant.So,What happens to cluster-based catalysts under real conditions of catalysis?Isomers may interconvert across barriers during catalysis.We use the method of constrained MD to study the cluster-catalyzed reaction under dynamic conditions.First,we studied the hydrogenation of CO2 to HCOO catalyzed by Cu13 clusters.The free energy and reaction energy barrier of the reaction were calculated under static and dynamic conditions,respectively.We find that the change of free energy with temperature under dynamic conditions is very different from that obtained under static conditions.In addition,calculations show that the change of reaction entropy with temperature takes the form of a Gaussian-like distribution.For such a huge entropy change,it usually occurs during the phase change.From this we studied the phase transition behavior of CU13 clusters in the initial state,transition state and final state of the reaction.Studies have shown that the solid-liquid coexistence interval and melting point of Cu13 clusters are different in different states.In addition,we selected Cu13 clusters to catalyze CO oxidation.At this time,four carbon monoxide molecules were adsorbed on CU13 clusters.In order to study the effect of CO coverage on the oxidation of CO catalyzed by CU13 clusters.Studies have shown that the differences in the phase transitions of Cu13 clusters in the initial state,transition state,and final state can well explain the relationship between the free energy and the reaction energy barrier with temperature under dynamic conditions.Studies have shown that the cluster structure changes in order to adapt to different species and coverage.In addition,the abnormal change in the free energy of the reaction is due to the entropy effect caused by the dynamic changes of the clusters.Our research provides a new perspective on understanding catalytic behavior under dynamic conditions.