The electrochemical performance and CO2 reduction mechanism on strontium doped lanthanum ferrite fuel electrode in solid oxide electrolysis cell

Abstract

Carbon dioxide reduction reaction on the fuel electrode is critical for CO2 conversion in solid oxide electrolysis cell, which is a promising technology to utilize CO2 and store electricity from intermittent renewable resources. This work presents a highly active electrocatalyst, strontium doped lanthanum ferrite (LSF), for direct CO2 reduction reaction, which is conducted in single cells with La0.9Sr0.1Ga0.8Mg0.2O3 as the electrolyte and La0.6Sr0.4Co0.2Fe0.8O3-δ as the air electrode. A current density of 0.76 A cm−2 is achieved at 800 °C and 1.5 V when pure CO2 is electrolyzed. By adding samaria-doped ceria to form composite fuel electrodes, the performance can be effectively improved. The current density increases from 0.76 to 1.06 A cm−2 while the total interfacial polarization resistance decreases from 0.26 to 0.12 Ω cm2. Furthermore, LSF exhibits high rate constant for CO2 reduction reaction, 1.04 × 10−4 cm s−1 at 700 °C. CO2 is favorable to form carbonate species on LSF surface, and the existence of carbonate species on LSF surface revealed by Raman spectra technique is further proved by DFT calculations. A proposed CO2 reduction mechanism is obtained, providing new insights into CO2 adsorption and dissociation on LSF surface.