Electrochemical Reduction of CO 2 in Water‐Based Electrolytes KHCO 3 and K 2 SO 4 Using Boron Doped Diamond Electrodes

The performance of Boron Doped Diamond (BDD) electrodes for the electrochemical reduction of CO 2 at room temperature and in water‐based electrolytes was investigated. Techniques such as linear sweep voltammetry, chronoamperometry, and chronopotentiometry were used to confirm the activity of BDD for the CO 2 reduction. Besides H 2 , CO and HCOOH were found as major products with CH 3 OH as a minor product. The effect of anionic species with and without buffer capacity was investigated using KHCO 3 and K 2 SO 4 as electrolytes. BDD did not show any degradation after using it in several experiments. The Faradaic efficiency (FE) for CO in the gas phase and the concentration of HCOOH in the liquid phase were higher in K 2 SO 4 than in KHCO 3 . However, the total FE for C 1 products was lower than 20%. Then BDD electrodes were modified with silver, which improved the FE for CO to 68% in K 2 SO 4 at −1.8 V vs. Ag/AgCl. Galvanostatic experiments were also performed for 10 hours at −10 mA cm −2 producing 30% FE for CO in the gas phase and 43,9 mM HCOOH in the liquid phase.