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/La0.6Sr0.4Cr0.9Co0.1O3-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.