Synthesis Of Ag-based Nanomaterials And Study On Electrocatalytic Properties Of CO₂ Reduction

Carbon dioxide is a common greenhouse gas that increasingly accumulates in the Earth’s atmosphere,causing global warming,rising sea levels,and the extinction of species.In terms of economic and social development,electrochemical techniques are usually used for carbon capture and storage,while combining with renewable energy to convert CO₂ into chemical products.Syngas is a very important and flexible chemical whose composition needs to be strictly controlled and adjusted to a specific CO/H₂ratio through a thermochemical conversion process to produce methanol or other alcohols,carbohydrates or hydrocarbons.At present,the catalysts used in the ECR mainly include non-metallic catalysts,such as carbon materials and metal catalysts,such as Au,Ag,Cu and so on.Metal Cu material can catalyze the conversion of CO₂to hydrocarbons and carboloy compound.It is the most widely studied metal catalyst at present.However,due to its own high initial potential,poor selectivity,hydrogen evolution and other serious problems.In contrast,metal Ag materials,with high catalytic activity and strong practicability,have been widely concerned.In this paper,Ag/Cu and Ag Cl:Ag catalytic systems were constructed by electrodeposition and photoreduction methods to reduce CO₂ into syngas.（1）By constructing Cu Ag bimetallic system and using the geometric effect and electron synthesis effect,based on the etched porous Cu,the hydrogen evolution reaction is inhibited by electrodeposition loaded with Ag.When the potential is-1.0 V,the ratio of CO:H₂ reaches 1.2:1.And as the potential increases,the ratio of CO to H₂continues to rise.Compared with nanoporous Cu catalysts,the bimetallic catalysts show higher activity and selectivity.There are a large number of unsaturated coordination active sites on the surface of porous catalysts,which reduce the adsorption energy of COOH*intermediates and facilitate the desorption of CO.Meanwhile,the particle structure of the catalysts itself is also conducive to the mass transfer of reactants and products.（2）Ag based catalyst has good CO selectivity,however,due to the low exposure of active sites in the reaction process,the traditional Ag based catalyst has some problems,such as low current density and high price.AgCl was used as the precursor by heat treatment and further photoreduction.Ag Cl:Ag catalyst can be prepared under control.From the stability test results,the catalyst surface is rich in Ag,indicating that a large number of Ag were reduced during the test.For Cl^-in the reaction process,it may interact with the*COOH intermediate through van der Waals force on the catalyst surface during the reaction process,thus reducing the adsorption energy of the intermediate.Compared with the pure Ag Cl:Ag catalyst,At the voltage of-1.0 V,the ratio of CO/H₂reaches 3:2 and the stability test for 7 h still maintains a high activity.