(112c) Electrochemical Exsolution of Metal Nanoparticles from Perovskite Oxide upon Electrolysis

This study offers a thorough exploration of the electrochemical reduction process of La_0.7Sr_0.2Co_0.2Fe_0.8O₃ (LSCF) perovskite during electrolysis, with a specific focus on understanding the exsolution mechanism of metal nanoparticles. The exsolution of these nanoparticles from perovskite electrodes plays a crucial role in enhancing their electrochemical performance during electrolysis. Through the application of cathodic polarization to the perovskite oxide electrode, it was observed that the exsolution process can be electrochemically induced within a remarkably short time frame, just a few minutes. Our investigation, including operando X-ray absorption near-edge structure analysis conducted during electrolysis, revealed a substantial reduction in the oxidation state of B-site atoms, particularly cobalt, within the LSCF electrode. Furthermore, it was observed dynamic changes in current density and area-specific resistance of the LSCF electrode during H₂O-CO₂ co-electrolysis (Figure 1(a)), which can be attributed to instantaneous alterations in electrical conductivity and surface adsorption properties due to exsolution of metal nanoparticles in response to variations in cell voltage. The electrochemical switching point, characterized by the transition from an increasing trend to a decreasing trend in area-specific resistance, was pinpointed marking a significant milestone in understanding the behavior of the LSCF electrode during electrolysis. Notably, electrochemically reduced LSCF (eRed-LSCF) electrode demonstrated outstanding stability and significantly reduced polarization resistance during electrolysis of H₂O and/or CO₂ (Figure 1(b)), without the need for a safety gas, highlighting its potential for practical applications.