A Study Of The Electrochemical Reduction Of Carbon Dioxide In Ionic Liquid Compounds

With the rapid development of economic today,large-scale of fossil fuel like oil and coal were widely used.As a result,the concentration of CO₂-the major component of greenhouse gases in atmosphere has been increasing significantly,leading to a serious threat to human survival and development.In order to effectively alleviate the greenhouse effect,the worrying people have been implementing basic state policies of resource conservation and environmental protection to achieve energy conservation and emissions reduction.On the other hand,CO₂ is regarded as a cheap,abundant C-1 resource industrial transformation.Yet the challenging part of utilizing the CO₂ resource properly involves the issue of CO₂ capturing.A low cost,high efficiency and recyclable CO₂ absorber seems to be the expected solution and has been studied extensively.Herein,a method involing taking advantage of excellent electrochemical properties of ionic liquids and superbase's super capacity of absorbing CO₂ was proposed.We select three ionic liquids,namely 1-ethyl-3-methyl imidazole tetrafluoroborate?[EMim]BF₄?,1-butyl-3-methylimidazoliumtetrafluoroborate?[BMim]BF₄?,1-hexyl-3-methylimidazolium tetrafluor-oborate?[HMim]BF₄?,and mix them with super base 1,8-diazabicyclo undec-7-ene?DBU?with different composite ratio respectively.It was found that with the increase of the proportion of the DBU in the ionic liquid compounds,CO₂ solubility increases accordingly.The electrochemical reduction of CO₂ at atmospheric pressure behavior in these ionic liquid compounds was studied.The results demonstrated that the process of CO₂reduction in both the single ionic liquid system and ionic liquid compounds,is subject to an irreversible one-electron process controlled by diffusion.Single ionic liquids and the corresponding ionic liquid compounds?IL/DBU?were characterized and their performance were tested,IR result showed,super base mixed with imidazole ionic liquid can capture proton of C-2 on imidazolium cation and formed a stable conjugate acid,and it will generate the corresponding carboxylic acid salts after mixing wiht carbon dioxide.A kind of amino-functionalized ionic liquid?[NH₂-pmim]BF₄?was also mixed with 1-ethyl-3-methyl imidazole tetrafluoroborate?[EMim]BF₄?,1-butyl-3-methylimidazolium tetrafluoroborate?[BMim]BF₄?,1-hexyl-3-methylimidazolium tetrafluor-oborate?[HMim]BF₄?in different rations to study the electrochemical reduction of CO₂.In these binary ionic liquids system,the presence of[NH₂-pmim]BF₄ enhances the capacity of CO₂ capturing.The binary ionic liquids system with exhibited a higher current density and a more positive potential for the reduction of CO₂ than those in pure traditional ionic liquid.As for EMim]BF₄/[NH₂-pmin]BF₄ and[BMim]BF₄/[NH₂-pmin]BF₄binary ionic liquids system,the idea weight percent of[NH₂-pmin]BF₄[NH₂-pmin]BF₄ was 0.4%,at which a relatively good electrochemical property was obtained,while for[HMim]BF₄/[NH₂-pmin]BF₄ 0.2%.