Synthesis of Carbon Monoxide in a Single-Chamber Electrolyzer Using a Boron-Doped Diamond Cathode

Carbon monoxide (CO) has high industrial value and can be obtained by the reduction of carbon dioxide (CO2), where electrochemical CO2 reduction represents a viable process to produce CO. Boron-doped diamond (BDD) is recognized as a suitable material for cathodes used in electrochemical CO2 reduction. The general strategy involves the use of a two-chamber electrolyzer separated by an ion-exchange membrane. However, the gaseous nature of CO enables its generation in a single-chamber flow cell, preventing its reoxidation to CO2 by continuous removal from the electrolyte. Furthermore, this would simplify the electrolyzer structure by avoiding expensive and degradable ion-exchange membranes. Here, we investigate CO production by using a single-chamber flow cell without an ion-exchange membrane. The best conditions after optimization (cell potential, counter electrode material, electrolyte, and cell thickness) resulted in a faradaic efficiency of about 58% at −1.9 V (vs. Ag/AgCl) for CO production with an IrO2 counter electrode in 0.1 M KClO4. Compared to two-chamber flow cells, the better faradaic efficiency, use of only one type of electrolyte, and avoidance of the use of an ion-exchange membrane make the single-chamber flow cell suitable for CO production by electrochemical CO2 reduction.