Quantifying Interface-Dependent Active Sites Induced by Topotactic Exsolution for CO₂ Electrolysis

Supported metal nanoparticles via in situ exsolution hold great promise for many fields including CO₂ electrolysis in solid oxide electrolysis cells. However, identifying and quantifying such in situ formed interfacial sites remain a challenge. Herein, we present a quantitative analysis of the inherent exsolution process and normalize the interfacial sites to the intrinsic activity of CO₂ electrolysis. CoFe/La_0.6Sr_0.4Cr_0.9Co_0.1O_3-δ (LSCC) interfaces are architecturally tailored by modulating the concentration of guest Fe cations, enabling precise control over the coverage of exsolved CoFe nanoparticles through a topotactic ion exchange strategy. The promotional role of Fe in facilitating Co cation exsolution is quantitatively investigated via X-ray absorption spectroscopy and Mössbauer spectroscopy. A quantitative correlation between the interfacial parameters of CoFe/LSCC and their intrinsic catalytic performance is well disclosed. CO₂ electrolysis performance is linearly positively correlated with the perimeter of the CoFe/LSCC interface, reaching a peak performance of 1.73 A cm^-2 at an optimal interfacial perimeter of 29.3 μm μm^-2. This study offers valuable insights into quantitative research on metal/oxide catalysts for CO₂ electrolysis.