Electrochemical operando TEM analysis of single gadolinia-doped ceria nanofiber

Nanofiber structures have been suggested for enhancing the electrode activity in solid oxide cells. In this work electrochemical operando TEM was applied on gadolinia-doped ceria nanofibers to investigate their conductivity and possible morphological and structural changes at operation conditions with relevance to solid oxide cells. Specifically, electrochemical impedance spectroscopy was performed on a single nanofiber inside an environmental TEM in 2.5 mbar O₂ at temperatures up to 600 °C. It is found that the CGO nanofiber structure changed when heating to 600 °C in O₂ by relative movements between individual grains leading to an increase in the fiber diameter and porosity. The activation energy extracted from EIS measurements in O₂ indicates that the conductivity is predominantly electronic. Such solid-state electrochemical operando experiments inside a TEM in reactive gases and at elevated temperatures can provide novel insights into complex process dynamics by simultaneous analysis of electrochemistry, structure and composition. These fundamental insights can yield structure-activity correlations with the potential to improve performance and durability of solid oxide electrolysis and fuel cells.