Voltammetric study of CO2 reduction at Cu electrodes under different KHCO3 concentrations, temperatures and CO2 pressures

The understanding of the electroreduction pathway of CO2 over Cu surfaces in KHCO3 solution is very important in the area of electrocatalysis. In this paper, we present linear sweep voltammetry results at different temperatures, different KHCO3 concentrations, and different CO2 pressures that provide important information about the CO2 reduction pathway. In experiments under CO2, at different temperatures, we obtained data that confirm the existence of COad as an intermediate of the reduction of CO2 over Cu surfaces. In addition, voltammetry experiments at KHCO3 concentrations between 0.01 and 2.0 M confirmed the theory that the increased pH created near the electrode surface during the reduction process is being lowered by the neutralization reaction by KHCO3. Also, we present a mechanism in which COad is displaced from the Cu surface in solutions pressurized with CO2 (30–250 psi or 2–17.2 bar). This model is based on voltammetric, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) results of experiments performed under different CO2 pressures.