A novel dual chamber (DC) measurement cell has been implemented for simultaneous monitoring of crystallographic and electrochemical (EC) properties of Ni-Ce_0.9Gd_0.1O_2−δ (Ni-GDC) solid oxide fuel cell (SOFC) anode at different fuel cell polarizations. The influence of system parameters (temperature, oxygen partial pressure in anode compartment and oxide ion flux through the electrolyte membrane from the cathode to the anode) on the crystallographic structure of GDC and redox performance of Ni has been studied. The oxide ion flux through the membrane from cathode to anode leads to increase of oxygen partial pressure in anode layers close to electrolyte. Increase of oxygen partial pressure leads to decrease of unit cell volume of the GDC lattice. The observed average change of GDC lattice parameter was 0.0147 Å V⁻¹ at 800°C. The oxidation of Ni caused by oxide ion flux at high fuel cell loads has been detected electrochemically but not from XRD results.

Ni-YSZ | YSZ | GDC | LSC single cells with different thickness of the electrodes have been prepared and studied at temperatures from 773 K to 1073 K. Single cells with high power density (~ 700 mWcm-2) and good time stability have been analyzed in detail using impedance spectroscopy data. Influence of the cathode thickness and synthesis temperature (i.e. porosity) on the rate limiting parameters has been demonstrated.

Characteristics of the porous Gd_0.15Sr_0.85CoO_3−δ and La_0.6Sr_0.4CoO_3−δ cathodes were compared using the data measured at different electrode potentials and oxygen partial pressures. The electrochemical high‐temperature in situ XRD (HT‐XRD) method combined with electrochemical impedance spectroscopy has been used. The response of the crystallographic parameters and impedance values on the changes of electrode potential has been discussed. Reversible changes of the lattice parameters for both cathodes, slower for Gd_0.15Sr_0.85CoO_3−δ compared with La_0.6Sr_0.4CoO_3−δ, were observed depending on temperature (T), electrode potential (E), and oxygen partial pressure (pO₂). The crystallographic parameters are determined by the vacancy formation kinetics as well as by vacancy formation energy in/at the cathode grain structure. Calculated impedance data were fitted to the experimental data and characteristics were obtained in context of crystallographic changes of the cathode materials studied.

In this study, the La/Sr ratio and A‐site deficiency of (La _{1− y} Sr _y ) _x Cr _0.5 Mn _0.45 Ni _0.05 O _{3− δ} (LSCMN) were systematically varied to investigate the effect of these modifications on lattice parameters, surface composition, and initial electrochemical performance. Studied materials were thermally treated in oxidizing and reducing gas environments and thereafter analyzed using X‐ray diffraction (XRD), time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS), and electrochemical analysis methods. X‐ray analysis of samples heat‐treated in air revealed that the La/Sr ratio influences the Mn ³⁺ /Mn ⁴⁺ ratio in LSCMN material, but the influence of A‐site deficiency is minor. After thermal treatment in a highly reducing environment, expansion of lattice parameters was observed, caused by the reduction of Ni ²⁺ to Ni ⁰ and partial reduction of Mn ⁴⁺ to Mn ³⁺ and simultaneous formation of oxide ion vacancies. The highest lattice changes were observed in the highest Sr concentration and at the 1%–3% A‐site deficiency range. The highest electrochemical activity was observed when the Sr content remained low ( y  = 0.2). The most stable systems had low A‐site deficiency. The study reveals that chemical and structural characteristics of the electrode surface, particularly the segregation of LSCMN components, play an essential role in the electrochemical performance and stability.