Electrocatalytic Reduction Of Carbon Dioxide In Quaternary Ammonium Salt / Organic Solvent Electrolyte

It is an important way to realize the large-scale development and utilization of renewable energy to convert CO₂ into methanol, which is used as a substitute for gasoline or basic chemical raw materials. At present, the most studied technological approaches is the electro-reduction of CO₂ to CO at first, and then CO is hydrogenated to methanol, preparation of CO and H2 required energy from renewable energy. The electrochemical reduction of CO₂ to CO is the key ideas of the above studies, for knowing more about this problem, this paper carried out the following research work:In the diaphragm electrolysis cell, KHCO₃ aqueous solution was used as the cathodic electrolyte to electro-reduction of CO₂, and the kinetic characteristics of CO₂ on gold electrode were studied. The results show that CO₂ can be reduced to carbon monoxide on the gold electrode in O.lmol/L KHCO₃ solution, but there are many problems, such as a strong hydrogen evolution reaction, low solubility of CO₂, electrodes are prone to lose activity. Electrode poisoning c 金 sed a sharp decline in the current density and current efficiency of carbon monoxide.CO₂ is a non-polar molecule, has low solubility in aqueous solution, and exist the problem of electrode poisoning deactivation, for which explored tetrabutyl ammonium perchlorate （TBAP）/propylene carbonate （PC） as an electrolyte electrochemical reduction of CO₂.The results show that comparing with reducing in KHCO₃ solution exist electrode poisoning deactivation, CO₂ can be stable electrochemical reduced to carbon monoxide in the electrolyte of 0.1mol/L TBAP/PC and there is no adsorbate on the electrode surface, no poisoning deactivation, CO generation current efficiency is stable. But there is also the problem of low current density, after a long time of electrolysis, there is a small amount of water in the cathode cell, which comes from the process of electro-reduction of CO₂ and the hydration of hydrogen ions which come from the water molecules. The electrochemical reduction of CO₂ will inevitably generate water, while the electrochemical reduction of CO₂ can not occur without the participation of water, the water in the anode chamber be oxidized to provide hydrogen ions to the cathode chamber. The electrochemical reduction of CO₂ in propylene carbonate is limited by the low current density. It is a reliable method to increase the migration speed of the hydrogen ion to enlarge current density.In the electrochemical reduction of CO₂ process will inevitably produce water, water has an important influence on the electrochemical reduction of CO₂, therefore selection of hydrophilic dimethyl sulfoxide as solvent, tetrabutylammonium perchlorate as electrolyte, the electrochemical behavior of CO₂ has been researched in TBAP/DMSO electrolyte. The results show that CO₂ can be well reduced to CO in TBAP/DMSO electrolyte. However, when the electrolyte temperature below 18 degrees Celsius, dimethyl sulfoxide easily crystallizes on the surface of the electrode, resulting in the working electrode losing of activity.Electrochemical reduction of CO₂ in organic electrolyte will be the main research direction, electrochemical reduction of CO₂ in the organic solvent electrolyte still exist the problem of low current density, researches about electrode materials and catalysts become the direction to solve this problem.