Sol–Gel Synthesis of CuO Nanoparticles and Its Use as Catalyst for Electrochemical CO2 Reduction

Copper and copper-based catalysts have been recognized as attractive heterogeneous catalysts for electrochemical CO₂ reduction. Herein, the synthesis of copper oxide (CuO) nanoparticles via a sol–gel process using agar as the dispersant agent followed by thermal annealing at 400, 600, and 800 °C is reported on. Evolution of chemical composition, morphology, and crystallinity of CuO nanoparticles in function the annealing temperature is examined. These CuO nanoparticles are assayed as catalysts for the CO₂ electrochemical reduction in a 0.1 m NaHCO₃ or 0.1 m KHCO₃ solution saturated with CO₂, generating hydrogen, carbon monoxide, formate, and acetate as products. Among the CuO catalysts assayed, the CuO-400 sample obtained at the annealing temperature of 400 °C leads to the highest formate production selectivity with a Faradaic efficiency of 26% at −0.9 V versus reversible hydrogen electrode.