Highly selective reduction of CO2 through a protonic ceramic electrochemical cell

Abstract

CO2 reduction has attracted widespread attention due to its critical role in the realization of carbon neutrality. Efficient conversion of CO2 to CO or CH4 via a protonic ceramic electrochemical cell (PCEC) is a good strategy. Herein, a promising electrochemical performance of CO2 reduction is achieved from a PCEC with a NdBa0.8Ca0.2Co2O5+σ (NBCC) air electrode, a BaZr0.4Ce0.4Y0.1Yb0.1O3-σ (BZCYYb) electrolyte, and a Ni-BZCYYb fuel electrode. A current density of 1.259 A cm−2 at 1.3 V is delivered when the fuel- and air-electrodes are exposed to 20% CO2–80% H2 and wet air with 3% H2O. A distribution of relaxation times analysis indicates that the rate-limiting step changes from the medium frequency region to the low-frequency region with the increase of the electrolysis current density. At 650 °C, the cells can typically produce CO at a production rate of ∼595 μmol min−1 cm−2 at 0.75 A cm−2 with high selectivity of over 99%, and a reasonable short-term stability has been demonstrated in a testing period of 100 h at 1 A cm−2.