Synthesis Of Au-based Nanomaterials And Their Research In Catalysis

Gold(Au)is one of the important precious metals.Because of its rich electronic structure and excellent catalytic properties,it is widely used in fuel cells,automobile exhaust treatment,organic hydrogenation,petroleum processing,biomass conversion and other fields.In the past few decades,a large number of synthesis methods have been developed,and the appearance,composition and performance regulation of Au nanomaterials have been achieved.However,there are new synthesis challenges,for example,in the process of synthesis,how to minimize the use of organic pollutants,make the synthesis process clean and simple.In terms of product structure,how to achieve structure and composition is more stable.In terms of catalytic performance,how to reduce costs while ensuring catalytic activity.As we all know,the catalytic performance of catalysts includes three aspects:catalytic activity,stability,and selectivity of catalysts.The factors that affect the catalytic performance of precious metal catalytic materials are electronic effects,geometric effects,and synergistic effects.The main goal of developing the synthesis method of developing new Au-base materials is to achieve a simple and clean constructor Au-base nanomaterials,and futher explores the structure composition of Au radical nanomaterials and surface modification.The impact of the catalytic activity and selectivity of the reaction mainly achieved the following results:1.We synthesized a series of low-loaded and highly active Au/CeO2-supported catalytic materials by impregnation method.The load of Au in Au/CeO2 supported catalytic materials can be effectively controlled by adjusting the addition amount of HAuCl4·3H2O.The results of catalytic oxidation of CO show that the Au/CeO2 catalytic material still shows high activity when the Au content is the lowest(0.2wt%).The temperature of 100%conversion of catalytic oxidation of CO is 60℃.This is mainly attributed to the electron transfer between CeO2 and Au and the generation of positively charged Au species(Auδ+).In addition,all the prepared catalysts showed a high BET surface area(140 m2·g-1).The large specific surface area provides sufficient adsorption sites for CO transformation.The low load of Au effectively reduces the cost of noble metal catalyst,which is beneficial to promote the industrial application process of this kind of materials.2.We synthesized Au nanoclusters on ceria(CeO2)supports using an in situ reduction method.Ultra-small Au nanoclusters were synthesized on the surface of CeO2 nanospheres by modification of sulfhydryl groups and and using sodium borohydride as reducing agent.The size of Au clusters was about 1.5 nm.Thiol chains were chosen to establish the link between ceria and Au NCs.On the one hand,the strong S-Au binding energy clearly contributes to the stabilization of Au NC.On the other hand,the formation of Au-S-Ce bond bridge has the advantage of improving the catalytic performance.The results of CO catalytic oxidation show that the presence of Au-S-Ce structure improves the electron transfer efficiency and makes the material exhibit high CO oxidation activity at room temperature.Moreover,due to the strong binding energy of S and Au,the material exhibits excellent stability during long-term operation.This strategy provides a new idea for designing stable supported Au nanocluster catalytic materials.3.We developed a one-pot wet chemical method for the synthesis of Janus structure Au-Mn3O4 composite nanocatalytic materials through the REDOX self-assembly of Au3+ and Mn2+ It is proved that the Au-Mn3O4 Janus structure can be achieved by a combination of REDOX self-assembly and Ostwald maturation process.It is found that the concentration of NH3·H2O is the main factor controlling the selective overgrowth and can control the coverage of Mn3O4 on the mesoporous gold surface.The results of the photocatalytic reaction of benzyl alcohol show that the activity of Au-Mn3O4 Janus structure in the photocatalytic oxidation of benzyl alcohol is significantly improved compared with the Au@Mn3O4 core-shell structure and Au-Mn3O4 mixture.4.Using cadmium sulfide nanowire as template and cation exchange strategy,we synthesized two kinds of Cu monatomic catalytic materials with different coordination structures.This strategy can change the coordination environment of Cu single atoms by regulating the different organics surrounding Cu-CD.In both materials,one Cu monatom has double coordination of sulfur(S)and nitrogen(N),while the other Cu monatom has only sulfur(S)coordination.The first shell coordination number of the central atom of Cu is 4,the structure of Cu-S/N-C is Cu-S1N3,and the structure of Cu-S-C is Cu-S4.The results of nitrobenzene hydrogenation show that the catalytic activity of Cu-S/N-C is better than that of Cu-S-C,that is,the S,N double modified Cu monatomic material has better nitrobenzene hydrogenation activity than only the S modified Cu monatomic material.It provides a feasible method to adjust the central metal coordination environment to improve the performance of monatomic catalytic materials.