In situ probing of voltage-driven metal exsolution in perovskite cathodes modulated by B-site composition

Voltage-driven metal exsolution from perovskite (ABO₃) cathodes is a promising strategy for developing high-performance solid oxide electrolysis cells (SOECs). However, the effect of B-site composition on the exsolution process remains unclear due to the lack of direct and in situ comparison of the key parameters influencing exsolution. Herein, a multi-electrode model cell with graded potential distribution was constructed using La_0.6Sr_0.4Co_xFe_1-xO_3-δ (x = 0.2, 0.4 and 0.6, denoted as LSCF28, LSCF46 and LSCF64) as cathodes. Coupled with in situ spatially resolved X-ray photoelectron spectroscopy (μ-XPS), the effect of Co/Fe ratios on voltage-driven exsolution behaviors was investigated under the same conditions. The in-situ and comparative characterization results reveal preferential exsolution of Co⁰ compared with Fe⁰ under applied voltage. Moreover, the overall metal exsolution rates and oxygen vacancy generation rates follow the order LSCF28 > LSCF46 > LSCF64, suggesting that the oxygen vacancy plays an important role in linking Co/Fe ratios to voltage-driven exsolution. This work provides mechanistic insights for optimizing SOEC electrodes and establishes an efficient in situ strategy for comparative studies of multiple material systems.