Electrocatalytic Reduction And Separation Of CO₂ By Organic Small Molecules

In the pa t century,the increasing population and the progress of science and technology have promoted the unprecedented increase of energy consumption,which has led to the increase of carbon dioxide level in the atmosphere and has seriously affected the natural environment on which human beings depend for survival.Therefore,it is important to limit emissions of carbon dioxide(especially from anthropogenic sources)and to reduce its atmospheric concentration.How to use suitable electrode material or catalyst to reduce CO2 and to capture large amount of CO2 and safely store CO2 to make CO2 into useful C substance have been the focus of scholars' resea rch.In this paper,different modified electrodes were prepared by electrochemical reduction and electrodeposition,and the redox behavior of 2,6-dimethyl-1,4-benzoquinone with and without CO2 was investigated by cyclic voltammetry and in situ infrared spectroscopy.At the same time,the electrochemical behavior of the catalytic reduction of CO2 on Pt electrode by 5-hydroxy-2-ariinopyridine was studied.The redox mechanism of CO2 under two different conditions was speculated.The main work was summarized as follows:1.Research progress of 2,6-dimethyl-1,4-benzoquinone and CO2 reduction on different electrodesTwo kinds of gold nanoparticles modified glassy carbon electrode(Au-NPs/GC and NG-Au/GC electrode)were prepared by electrochemical reduction and electrodeposition to constructed different electrochemical interfaces.The cyclic voltammetry and EIS results showed that the Au-NPs/GC electrode prepared by electrochemical reduction of 400s time has better electrochemical activity than the gold electrode and the glassy carbon(GC)electrode and the NG-Au/GC electrode.The redox behavior of 2,6-dimethyl-1,4-benzoquinone(DBQ)with or without CO2 on different electrodes was studied by cyclic voltammetry and field infrared spectroscopy.The results of ?Ep at different electrodes show that DBQ on Au-NPs/GC electrode has faster electron transfer rate.The experimental results at different electrodes show that the possible redox mechanism of DBQ on these electrodes was proposed that DBQ obtained an electron to form a semi-quinone radical,and then obtained an electron to form a divalent anion.Later,the redox mechanism of DBQ with CO2 on different electrodes was studied.It was found that the CV behavior was changed when under the condition of CO2,and the two pairs of redox peaks became a pair of redox peaks.Combined with the corresponding fast scanning infrared 3D image,it is inferred that DBQ obtained an electron to form a semi-quinone radical,and then CO2 attacks the carbon next to the carbonyl group,and then obtained an electron to form a divalent anion.2.Progress in Catalytic reduction of carbon dioxide with 5-hydroxy-2-aminopyridineFirstly,the electrochemical behavior of 5-hydroxy-2-aminopyridine solution on different electrode(Au and GC and Pt)was studied.When CO2 was not incorporated into HA aqueous solution,the cyclic voltammetry at different electrodes showed that there was no electrochemical redox phenomenon when the potential window was-0.2?-0.8V.However,a pair of apparent redox peaks were observed on Pt electrode after HA solution saturated with CO2.By studying the CV diagram at different scanning speeds,we can clearly see that the square root of the sweep velocity and the reduction current density show a good linear relationship.The linear equation is y=-0.11x-0.33,R2=0.990,which is in line with the linear diffusion equation.The linear equation is ip=(2.69×10-5)n3/2AD01/2C0V1/2.It shows that the reaction process is a quasi-reversible reaction controlled by diffusion.Combined with the results of the in situ IR spectra of the multiloop scanning electrochemistry,it can be confirmed that the reaction is reversible.Furthermore,the electrochemical behavior of 2-aminobenzimidazole in the reduction of CO2 was studied in the same way.The results of IR and CV were in agreement with the experimental results and had the same ability to catalyze CO2.F inally,the voltammetric behavior of 2-mercaptobenzimidazole and 4-dimethylaminopyridine on Pt electrode for catalytic reduction of CO2 was studied.The results show that both compounds can reduce CO2 at the potential of-0.2V?0.8V,and the mechanism is the same as that of the former two compounds.The results of reduction of CO2 over organic base catalyst were consistent with those reported in the literature.The above conjecture was further verified by in situ infrared spectroscopy.