Electrochemical Reduction of CO₂ in Water-Based Electrolytes KHCO₃ and K₂SO₄ Using Boron Doped Diamond Electrodes

The performance of Boron Doped Diamond (BDD) electrodes for the electrochemical reduction of CO₂ 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 CO₂ reduction. Besides H₂, CO and HCOOH were found as major products with CH₃OH as a minor product. The effect of anionic species with and without buffer capacity was investigated using KHCO₃ and K₂SO₄ 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 K₂SO₄ than in KHCO₃. However, the total FE for C₁ products was lower than 20%. Then BDD electrodes were modified with silver, which improved the FE for CO to 68% in K₂SO₄ 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.