(Invited) Selective CO2 Conversion in Protonic Ceramic Electrochemical Cells

Abstract

Protonic ceramic electrochemical cells (PCECs) are solid-state electrochemical devices that employ proton-conducting oxides as electrolytes, which offer a promising approach for electrification of chemical manufacturing, including CO2 reduction to produce value-added chemicals. The primary advantage of PCECs is their intermediate operating temperatures (300-600 °C), which thermodynamically and kinetically favor the CO2 reduction chemistry at the negative electrode. Unfortunately, the conventional negative electrode of PCECs, such as BaZr0.8-xCexY0.2O3- \U0001d6ff-Ni or BaZr0.8-xCexY0.1Yb0.1O3- \U0001d6ff-Ni, cannot reduce CO2 to either CH4 or CO with a selectivity of >99%, leading to the production of a mixture of CO and CH4. In this talk, we will present the rationally designed negative electrodes for CO2 conversion PCECs. The PCECs equipped with the new negative electrodes selectively favor the CO2-to-CO conversion. A selectivity of ~100% toward CO has been demonstrated over a wide range of operating temperatures (400-600 °C) and applied potential/current density. The negative electrode demonstrated in this work fully suppresses the CH4 production. In situ diffuse reflectance infrared spectroscopy (DRIFTS) was performed to probe the CO2 reduction mechanisms over the negative electrodes. This work validates that PCECs equipped with the rationally designed negative electrode can selectively manufacture chemicals.