Operando Electron Microscopy and Impedance Analysis of Solid Oxide Electrolysis and Fuel Cells

Operando transmission electron microscopy (TEM) integrated with electrochemical impedance spectroscopy (EIS) is applied to the analysis of a model solid oxide electrolysis/fuel cell (SOEC/SOFC). The cell features electrodes made of gadolinia-doped ceria (CGO) and an electrolyte of yttria-stabilized zirconia (YSZ). Fabricated through pulsed laser deposition (PLD) and subsequent FIB-SEM processing procedures, the model cells were mounted on MEMS chips for operando TEM. Testing was carried out in an environmental TEM (ETEM) under reactive gases (H2 and H2O) at elevated temperatures relevant for SOEC and SOFC operation and under applied electrical potential. The activation energies for the YSZ ionic transport and CGO surface reaction were found to be 0.9 and 0.5 eV, respectively, aligning with literature values. The work demonstrates the feasibility of conducting SOEC/SOFC full cell tests directly within the ETEM, including EIS analysis during cell operation, offering deep insight into the cell contributions: electrochemical reactions, transport, and degradation mechanisms.