Electrolysis Products Of Carbon Dioxide In Molten Carbonates

Increasing carbon emission is one of the main reason that causes intensified greenhouse effect and frequent extreme weather.Carbon fixture technology such as capture,storage and conversion of carbon dioxide are effective ways to reduce carbon emission.Electrolysis of carbon dioxide in molten salt is a kind of extremely popular choice among conversion technology.It shows high reaction rate and can product high value-added carbon material or CO and O2 and make use of renewable energy source like solar and wind power,thus making it green and clean.Researching the gas product and mechanism of the reaction on the anode and cathode have great significance on this technology.This thesis developed an automated on-line detection devices for electrolysisof carbon dioxide in ternary carbonate(Li2CO3-Na2CO3-K2CO3)and analyzed the products of the anode and cathode under different conditions.And the application of carbon material in the lead acid battery was studied at the same time.The conclusion is as follows:A set of U-shaped automated on-line detection devices was designed to study electrolysis of carbon dioxide in molten carbonate,of which the anode and cathode is separated.The material of reactor was chose and evaluation.It found that,as material of reactor,titanium material could operate stable for 1000h at 450? in ternary carbonate.The interaction between Ti and gas products of CO2 conversion was further studied by the Thermogravimetric Analysis.The weight of the Ti reactor surface increased 7.15×10-11g/s per square centimetre.The results illustrated that the influence of titanium reactor to the gas product detection in the experiment can be neglected.The experiment also confirmed the time for the equipment to replace the gas,time for electrolysis and the rate of flow of the gas,and optimized the design of gas pass system,choice of material and size for anode and the fabrication of reference.The product of anode derived from electrolysis of carbon dioxide at 450 ? in ternary carbonate was studied by using the system when the anodic polarization potential and gas atmosphere in the cathode camber were different.When gas atmosphere in the cathode camber contained carbon dioxide and.the anodic polarization potential was 0.7 to 1.1V(vs.Ag/Ag2SO4),carbon dioxide and oxygen could be detected in the anodic camber.The volume ratio of CO2 and O2 was between 1 to 2 and the ratio and current density increased as the potential moved positively.It illustrated that the oxygen in the anode was from oxidation of the carbonate ions and oxygen ions and the oxidation of the carbonate ions was the main reaction.It found that the volume ratio of carbon dioxide and oxygen increased when electrolysis for along time.Let the system stand for a long time,the oxygen anion around the cathode spread to the anode,making the capture ability of the molten salt recovered.In pure argon atmosphere,only oxygen could be detected when the anode potential changed from 0.7V to 0.9V and carbon dioxide was detected above 0.9V.The volume ratio of carbon dioxide and oxygen was between 0 and 0.5.The oxidation of oxygen ions was the main reaction.That was because there was no carbon dioxide supply in the cathode camber.The oxygen anion around the cathode migrated to the anodic and involved in the oxidation of anodic electrode to produce oxygen or combined with carbon dioxide produced by the anode.The product of cathode for electrolysis of carbon dioxide in molten salt can be carbon or CO.The product of cathode was studied by using the new system when the cathode material and current density were different.Carbon monoxide was not detected no matter the cathode material was nickel,titanium or stainless steel in galvanostatic text when the cathode current density range from 15 to 200 mA/cm2.It illustrated that CO could not be produced at the rate that could be detected for the material and current density researched.Carbon was the main product of the cathode.The results provided reference for the pilot and scale-up equipment and the design of the tail gas absorption equipment.For carbon materials produced by electrolysis of carbon dioxide in molten carbonate,the activation effect of the lead battery was studied.The result showed that compared with acetylene black and carbon nanotube,the new kind of carbon powder produced by molten carbonate could improve quantity of electric charge and current efficiency of the process remarkably.The existence of carbon material promoted the conductivity of the system and inhibited the generation of large particles of sulfate crystals.From the electrochemical experiment,it convinced that carbon material produced by molten salt could be a new kind of activator with great potential.