关键词: H型电解池, 质子交换膜, 二氧化碳, 电化学还原, 析氧反应

Abstract:

Electrochemical reduction of carbon dioxide (CO₂) was studied in the H-type electrolytic cell. It was found that the voltage between the cathode and the anode would increase during the long time electrolysis process, for this reason the electrolytic process would be unsustainable. After the experimental investigations carried out by constant potential electrolysis, constant current electrolysis, pH test and KHCO₃ concentration analysis of anode electrolyte before and after the electrolysis, the increase in cell voltage might be caused by the following process: H⁺, that was generated from the anodic oxygen evolution reaction, reacted with HCO₃^- to form water and CO₂, and the HCO₃^-in the anode chamber was consumed; then K⁺ in the anode chamber was forced to spread into the cathode chamber which led to the decrease of the electrolyte concentration in the anode chamber. Therefore, the conductivity of the electrolyte solution in the anode chamber decreased, resulting in the rise of the anode potential. This phenomenon may happen in the alkaline electrolyte in an anode cell, therefore, in order to ensure the electrolysis process sustainable and keep high energy conversion efficiency, the anode electrolyte cannot be any alkaline substance.

Key words: H-type electrolytic cell, proton exchange membrane, carbon dioxide, electrochemical reduction, oxygen evolution