Theoretical Computational Study On Structure Regulation And Performance Optimization Of Noble Metal-based Nanocluster Catalysts

The development of efficient nanocatalysts is one of the effective ways to solve energy shortage and environmental pollution.With the rapid development of nanotechnology,noble metal-based nanoclusters have attracted extensive attention in the field of catalysis due to their unique physical and chemical properties.For example,the alloyed nanoclusters of noble metals and cheap metals,especially the alloy nanoclusters of "crown jewel" structure,can greatly improve the electrocatalytic activity while saving cost,which is an important research topic in the field of catalysis.In addition,the core-shell structure of noble metal clusters as core components is also another means to improve the catalytic activity.For example,the clusters of noble metal-semiconductor core-shell structure show excellent optical properties and photocatalytic performance.Therefore,noble metal-based nanoclusters are worthy of in-depth study as promising nanocatalysts,which are expected to play an important role in alleviating energy shortage and environmental governance problems.Based on the above reasons,the first-principles method based on density functional theory combined with molecular dynamics simulation method is used to study the structural,catalytic,optical and electronic properties of noble metal-based nanocluster catalysts.The specific research contents are as follows:(1)In this paper,a series of platinum-based alloy clusters with "crown jewel"structures are designed.Through the first-principles calculations,the oxygen reduction catalytic activity and thermodynamic stability of these platinum-based clusters with crown jewel structure are systematically studied.The results show that PtCu alloy cluster shows the comparable or even better ORR activity than Pt catalyst,and the structure also has high thermodynamic stability.By analyzing the electronic properties,the changing of the oxygen adsorption energy and oxygen reduction catalytic activity of these alloy clusters are explained.Finally,a descriptor coupled with valence electrons and Bader charges is constructed to further explore the correlation between electronic structure and catalytic activity,which can be used to accurately predict the oxygen reduction catalytic activity of alloy clusters.(2)The catalytic activity of the "crown jewel"-structured PdCu alloy cluster for hydrogen evolution reaction and oxygen reduction reaction is calculated by the first-principles method,and the reason for the high catalytic activity is explained by analyzing the electronic structure.Since the synthesis of nanoclusters usually requires a high calcination temperature,the heating process and thermal stability of crown jewel-structured PdCu clusters are investigated by molecular dynamics methods.Interestingly,a structural transition from cuboctahedral structure to icosahedral structure is found in PdCu alloy clusters.Finally,the effects of cluster sizes and shapes on these properties are discussed.(3)Structural stability is an important indicator to characterize the catalysts,and the structural evolution directly affects the activity of the catalyst,which is essential for designing efficient catalysts.The heating process of different types of PdCu clusters is simulated by molecular dynamics method.The effects of cluster size,composition and element concentration on the thermal stability and structural evolution of PdCu clusters are investigated.Then,the conditions and influencing factors of the structural transformation for PdCu clusters from cuboctahedral to icosahedral are studied.Finally,the reason for the icosahedral structural transformation is discussed by calculating the excess energy.(4)The noble metal core in the noble metal-semiconductor core-shell structure plays an important role in the catalytic activity of the nanostructure.The size effect of the noble metal core and the noble metal-semiconductor interlayer interaction can be used as means to modulate the activity.The structural,optical and electronic properties of a series of Agn@(ZnS)42(n=6-16)core-shell nanoclusters are investigated by first-principles calculations.By calculating the absorption coefficient,it is found that the Ag@ZnS core-shell structure exhibits higher visible light absorption and red-shifted in the UV-Vis absorption spectrum compared with the ZnS structure,thereby enhancing the visible light catalytic activity.This study paves a way for improving the visible light catalytic activity of ZnS structure.