Electrochemical reduction of CO2 to methanol with synthesized Cu2O nanocatalyst: Study of the selectivity

The selectivity of a particular product over possible multiple products and their quantitative distribution in the electrochemical reduction of CO2 has been investigated. The generation of products and the said distribution depend on the various methods and materials like catalysts, electrodes, electrolytes, selectively proton permeable membrane used in the reduction process, numbers of available hydrogen ions at the cathodic catalytic surface and its adsorption characteristics on the catalysts surface dispersed on the cathode. Copper (Cu) and cuprous oxide (Cu2O) nanocatalysts have been synthesized and characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Field Emission Scanning Electron Microscopy (FESEM) for finding the differences in their surface characteristics in order to explain the selectivity of product in their use as catalysts. The efficacy of the reduction process with the synthesized catalysts is studied in the customized electrolytic cell. Methanol is selectively produced by using Cu2O nanocatalyst as a cathode in an aqueous electrolyte, potassium bicarbonate (KHCO3), whereas methane and ethylene are formed predominantly with Cu nanocatalysts. The cathodic potential applied to the electrolytic cell with Cu2O as a catalyst on the cathode is optimized at −2.0 V vs. SHE for both the methanol selectivity and also for the minimization of undesired hydrogen evolution. The maximum faradaic efficiency of 47.5% for methanol at a maximum current density of 7.8 mA cm−2 is obtained with a sustained current density of 5.6 mA cm−2 at a run time of 50 min.