Solid oxide cells (SOC) are high-temperature electrochemical device that show promise for clean energy production by converting hydrogen and air into electrical power (fuel cell mode) and vice versa (electrolysis mode). The efficiency of the electrochemical reactions depends on the microstructure and the material properties of both the porous oxygen and hydrogen electrodes. These materials are subject to extreme environments during operation at high temperatures and under polarization. Understanding changes to the electrode material itself can provide valuable insights into the long-term feasibility (e.g. stability / structural stability / performance) of solid oxide cells for industrial applications. 

In this work, we analyzed with local atom probe tomography (APT) a composite oxygen electrode made of Lanthanum doped Strontium Cobalt Ferrite (LSCF) and Ceria doped Gadolinium Oxide (CGO). Atom probe tomography provides compositional information with near-atomic spatial resolution in three dimensions. In the analysis of this LSCF-CGO composite, a reference sample and a sample aged in electrolysis mode at 800 °C were analyzed. Figure 1a shows the 3D ion distribution of an interface between the CGO and LSCF phases. Figure 1b shows a proximity histogram [2] of the concentration gradients at the phase boundary into each distinct phase. In several datasets, grain boundaries were observed in the ceramic electrode and APT was able to demonstrate enrichment of Fe, Co, and Sr at the boundaries (Table 1).

In both samples, a strong interdiffusion was highlighted between the LSCF and CGO grains. More specifically, a diffusion of Gd into the LSCF material was evidenced that could affect the electrode performance and the phase stability. Therefore, the atom probe tomography can provide valuable insights into the efficiency of solid oxide cell materials and long-term behavior under typical operating conditions at high temperatures.