Application And Research Of Copper Fund Nanomaterials In Electrocatalytic Reduction Of Carbon Dioxide

Excessive consumption of traditional fossil energy has led to a rapid increase in total carbon dioxide emissions,causing various global problems:greenhouse effect,sea level rise,extreme weather,etc.Therefore,it is very important to convert carbon dioxide into high value-added products to relieve energy and environmental pressure.Among the methods of photochemistry,electrochemistry,thermochemistry and biochemistry,electrocatalytic carbon dioxide reduction reation（CO₂RR）is a new type of catalytic technology that converts CO₂into valuable chemical substances and fuels with broad prospects.This reaction uses renewable electric energy as an energy source,and the reaction can occur under normal temperature and pressure conditions,which can realize the use cycle of a new type of hydrocarbon energy-carbon dioxide.Copper-based catalysts have many advantages such as low cost and various hydrocarbon products,and therefore have attracted wide attention from scientists.However,the electrocatalytic reduction of copper-based catalysts has a high overpotential,low catalytic activity,poor selectivity and other problems,so it is necessary to improve the activity,selectivity and stability of copper-based catalyst.In this paper,copper-based catalysts are used as research objects.Two types of copper-based nanocatalysts:Cu₂O/In₂O₃ bimetal oxide catalyst and copper-nitrogen-carbon（Cu-N-C）composite nanocatalyst are designed by adjusting the catalyst material composition,regulating micromorphology,and doping with bimetals to improve the activity,selectivity and stability of copper-based catalysts.Raman,XRD,XPS,SEM and other material characteriza tion methods are used to characterize the structure and morphology of the prepared nanocatalyst;electrochemical workstations were used for CV,LSV and other electrochemical performance tests;gas chromatography and nuclear magnetic resonance technology were used to reduce CO₂ for analysis.The specific work content of this paper is as follows:（1）In the third chapter,we prepared cubic Cu₂O,In₂O₃ single metal oxide catalyst and cubic Cu₂O/In₂O₃ bimetal oxide catalyst by solvothermal method.Electrocatalytic carbon dioxide reduction products of Cu₂O and In₂O₃ single metal oxide catalysts are mainly HCOOH,the optimal faraday efficiency is 51.2%（-0.63 V vs.RHE）,90%（-0.81 V vs.RHE）;electrocatalytic carbon dioxide reduction products of Cu₂O/In₂O₃ bimetal oxide catalyst is mainly CO.When the initial feed ratio of copper acetylacetonate/indium acetylacetone is 15:1,CO has the highest faraday efficiency of 90.8%（-0.58 V vs.RHE）;After electrolysis at constant potential-0.58 V（vs.RHE）for 20 h,the current density can still maintain about 90%and the catalysts has good electrocatalytic stability.（2）In the fourth chapter,we adopt a simple,low-cost one-pot method,using polyacryloni trile oligomer（LPAN）pre-oxidized powder as the matrix material,copper nitrate trihydrate（Cu（NO₃）₃·3H₂O）as a copper source,added Kechen Black and calcined at high temperature to form a metal Cu-doped porous nano-carbon-based catalytic material（Cu-N-C）.The micromorphology of Cu-N-C catalyst is a relatively uniform circular plate with a particle size of about 60-90 nm.Different ratios of Cu/N-C have greatly different activities and selectivities.Among them,the composite catalyst with the initial feed ratio of Cu/N-C of 1:20has the best performance.At a constant voltage of-1.03 V（vs.RHE）,the faraday efficiency of electrocata lytic carbon dioxide reduction reation to formic acid is 72.5%.After electrolysis 20 hours,the current density remains 89.9%and the attenuation is small.Therefore,the Cu-N-C composite catalyst has good catalytic activity and catalytic stability.The nano-carbon-based catalytic material exhibits excellent catalytic performance,probably because the carbon-based material uses polyacrylonitrile oligomer（LPAN）pre-oxidized powder as the base material,and the nitrogen（N）element in LPAN exists in the form of chemical bonds,it has natural advantages;Secondly,the porous carbon-based materials greatly increase the specific surface area of Cu-N-C catalyst,and expose more active sites,so can greatly improve the catalytic activity of the catalyst.Comprehensive research shows that the prepared Cu₂O/In₂O₃ bimetallic oxide catalyst and copper-nitrogen-carbon（Cu-N-C）composite nanocatalyst both have excellent electroca talytic CO₂ reduction performance.At the same time,the catalyst synthesis process is simple,low the cost and pollution-free.Therefore,the results of this paper can provide effective methods and ideas for improving the activity,selectivity and stability of copper-based catalysts.