Ag-Based Nanomaterials For The Conversion Of Gas Small Molecules

With the rapid development of the economy,people's demand for energy is increasing.As a non-renewable resource reserve,fossil fuels are in urgent need of finding a sustainable energy production chain.Due to the large number of small molecules in nature(such as hydrogen,oxygen,carbon dioxide,nitrogen,etc.),the study of small molecule gas conversion has become a very promising research direction.The gas small molecule conversion reaction includes oxidation reaction,reduction reaction,reforming reaction and coupling reaction,the reaction forms include thermal catalysis,photocatalysis,and electrocatalysis,which can realize conversion between small molecular gases,and can also be used to prepare useful liquid chemical.This research has great practical significance for the sustainable development of energy and green chemistry.Therefore,it is necessary to design a suitable catalyst to increase the activity of the reaction and improve the reaction efficiency as much as possible.Metallic silver is very suitable for use as a catalyst due to its good electrical conductivity,surface effect and size effect.However,due to its low chemical reactivity,it is necessary to form an alloy to exert its advantages.Silver can be alloyed with most other elements of the periodic table except hydrogen,lithium and lanthanum.Through the alloy effect and the characteristics of electrons easily transferred by silver,the amount of active sites can be increased,thereby facilitating the catalytic activity of the reaction.In this paper,we introduce the synthesis of some silver-based materials and carry out in-depth characterization,explore the catalytic activity of silver-based materials on the gas small molecule conversion reactions.Including:heterogeneous CuAg nanoparticles catalyzed water gas shift reaction with adjustable composition ratio,PdAg alloy nanoparticles with adjustable composition ratio and size used for direct synthesis of hydrogen peroxide,and core/shell Ag/SnO2 nanoparticles with adjustable shell thickness are used for carbon dioxide electroreduction.The main contents are as follows:Chapter 1.This part briefly introduces the research progress of small molecule gas conversion,the reaction mechanism of partial reaction,the design of catalyst and the idea of improving performance,and clarifies the basis and research content of this paper.Chapter 2.The heterogeneous CuAg nanoparticles with adjustable composition ratio was obtained by a simple one-step method.The growth process and interface structure were studied by a series of characterization methods.The catalytic performance of the water gas shift reaction was studied.Chapter 3.The PdAg alloy nanoparticles with adjustable size and composition ratio were synthesized by a simple one-step method,and the performance of the material for direct synthesis of hydrogen peroxide was studied.Among them,the electron transfer caused by the alloy effect between Pd and Ag is the key to high performance.Chapter 4.A series of Ag/SnO2 core/shell nanoparticles with adjustable shell thickness were successfully synthesized by two-step temperature change method,and the CO2 reduction reaction was studied.The optimized ones exhibited very high Faraday efficiency of carbon monoxide and formic acid.The reason for the high activity was mainly because the silver on the core was incorporated into the surface SnO2,which caused the surface to change the binding energy of the reaction intermediate to improve the performance.