Selection of suitable organic electrolyte for CO2 electro-reduction to CO in three-compartment electrolysis cell with NaOH and Cl2 yielded as byproducts

Abstract

Developing high performance electrolyte is essential in improving the performance of CO2 electro-reduction. In this work, we have constructed a three-compartment electrolysis cell for CO2 reduction to CO in organic electrolyte, with NaOH and Cl2 produced as byproducts. The generated CO and Cl2 can be served as feedstock for the production of phosgene, which is a widely used acylating agent for producing valuable downstream products. In order to improve the performance of the electrolysis cell, various commonly used organic solvents and supporting electrolytes were investigated. Consequently, 0.72 M Bu4NCF3SO3 in propylene carbonate (PC) was selected due to its high CO2 solubility. This electrolyte enabled the achievement of a current density of 27 mA/cm2 at a potential of −2.0 V (vs. SHE), with a stable Faradaic efficiency of 93 % for CO production. Compared with an aqueous catholytes, the altered double electric layer in the organic electrolyte prevents cathode poisoning, which is crucial for practical applications.