Pulsed electrochemical synthesis of formate using Pb electrodes

Abstract

Lead cathodes show decreasing Faradaic Efficiency (FE) in electrochemical conversion of CO2 to formate, favoring hydrogen, within minutes of operation in KHCO3 electrolyte at −1 to −1.3 V vs RHE. Periodic anodic polarization (pulsed electrochemistry) is demonstrated to result in a high time-averaged FE towards formate. Specifically, an anodic polarization time of 0.1–1 s is sufficient to obtain a Pb-surface providing an averaged formate FE of 30–50%, when the cathodic polarization time is limited to a few seconds. A Pourbaix diagram and Raman spectra are provided, which show that PbCO3 is formed on the surface of the cathode in KHCO3 electrolyte at anodic potential (0.05 V vs RHE), which compound is likely inducing the high FE towards formate. Our method thus provides a means to operate Pb electrodes in electrochemical CO2 reduction with high stability, at a low energy penalty.