Comparison of different infiltration amounts of CeO2 inside Ni-YSZ anodes to improve stability and efficiency of Single-Chamber SOFCs operating in methane

Electrochemically active oxide-based anodes capable of working in Single-Chamber Solid Oxide Fuel Cells (SC-SOFCs) were developed. Their performance is related to the selectivity of the electrodes. Tests are carried out on lab-scale devices with YSZ pellets as solid electrolytes in electrolyte supported cells. Selecting methane as a fuel, a gas mixture in the ratio CH4/O2 = 2 was chosen. The Ni-YSZ (NiO:YSZ=60:40) anode was optimized through CeO2 nanocatalysts infiltration to enhance the anode catalytic activity and make its reduction easier. Several infiltration amounts were compared, from null to 15% of the electrode weight. Both symmetric and complete cells (with LSCF-based cathodes) were tested in H2 and CH4/O2. For increasing amounts of infiltrated CeO2, symmetric cells tests describe an area specific resistance (ASR) reduction from 40 Ω cm2 to 1.7 Ω cm2 in hydrogen and from 11 Ω cm2 to 3.9 Ω cm2 in the methane/oxygen mixture. While complete cells tests displayed an ASR drop from 30 Ω cm2 to 2.9 Ω cm2 in H2, and from 8.7 Ω cm2 to 4.3 Ω cm2 in the methane/oxygen mixture, while OCP and power grew from 478 mV and 3.7 mW cm-2 to 766 mV and 13 mW cm-2.

Electrochemical properties of La9.33Si6O26(LSO)-La0.8Sr0.2Ga0.8Mg0.2O2.55(LSGM) electrolyte over NiO and La0.1Ca0.9MnO3(LCM) electrodes

The electrochemical properties of La9.33Si6O26(LSO)-La0.8Sr0.2Ga0.8Mg0.2O2.55(LSGM) electrolyte composites have been evaluated over NiO and La0.1Ca0.9MnO3 (LCM) electrodes using symmetric and asymmetrical cells of NiO/LSO-LSGM/NiO and NiO/LSO-LSGM/LCM, respectively. The Nyquist plot obtained from this study suggested that the new electrolyte system exhibits excellent performance over the NiO and LCM electrodes and shows an ideal Randel cell electrical circuit characteristic in both NiO/LSO-LSGM/NiO and NiO/LSO-LSGM/LCM cells. The area-specific resistance (ASR) and, the activation energy (Ea) of NiO/LSO-LSGM/NiO from the Arrhenius plot are lower than the NiO/LSO-LSGM/LCM, which is 0.30 Ω cm-2 and of 0.74 eV versus 0.40 Ω cm-2 with Ea of 0.76 eV, respectively.

On the High-Temperature Oxidation and Area Specific Resistance of New Commercial Ferritic Stainless Steels

Two commercial ferritic stainless steels (FSSs), referred to as Steel A and Steel B, designed for specific high-temperature applications, were tested in static air for 2000 h at 750 °C to evaluate their potential as base materials for interconnects (ICs) in Intermediate Temperature Solid Oxide Fuel Cell stacks (IT-SOFCs). Their oxidation behavior was studied through weight gain and Area Specific Resistance (ASR) measurements. Additionally, the oxide scales developed on their surfaces were characterized by X-ray Diffraction (XRD), Micro-Raman Spectroscopy (μ-RS), Scanning Electron Microscopy, and Energy Dispersive X-ray Fluorescence Spectroscopy (SEM-EDS). The evolution of oxide composition, structure, and electrical conductivity in response to aging was determined. Comparing the results with those on AISI 441 FSS, steels A and B showed a comparable weight gain but higher ASR values that are required by the application. According to the authors, Steel A and B compositions need an adjustment (i.e., a plain substitution of the elements which form insulant oxides or a marginal modification in their content) to form a thermally grown oxide (TGO) with the acceptable ASR level.

Femtosecond Laser-Induced Surface Modification of the Electrolyte in Solid Oxide Electrolysis Cells

Electrolyte-supported solid oxide cells are often used for steam electrolysis. Advantages are high mechanical stability and a low degradation rate. The aim of this proof of concept study was to use a femtosecond laser to process the electrolyte of an electrolyte-supported solid oxide cell and evaluate the effect of this laser treatment on the electrochemical performance. The femtosecond laser treatment induces a macroscopic and a superimposed microscopic structure. It can be proven that the electrolyte remains gas tight and the electrochemical performance increases independently of the laser parameters. The initial area-specific resistance degradation during a constant current measurement of 200 h was reduced from 7.9% for a non-treated reference cell to 3.2% for one of the laser-treated cells. Based on electrochemical impedance measurements, it was found that the high frequency resistance of the laser-treated cells was reduced by up to 20% with respect to the reference cell. The impedance spectra were evaluated by calculating the distribution of relaxation times, and in advance, a novel approach was used to approximate the gas concentration resistance, which was related to the test setup and not to the cell. It was found that the low frequency polarization resistance was increased for the laser-treated cells. In total, the area-specific resistance of the laser-treated cells was reduced by up to 14%.

From theory to experiment: BaFe0.125Co0.125Zr0.75O3−δ, a highly promising cathode for intermediate temperature SOFCs

BaFe0.125Co0.125Zr0.75O3−δ perovskite is a novel and efficient MIEC electrode for IT-SOFCs. Symmetrical cells with an area-specific resistance of 0.13 Ω cm2 at 700 °C and 0.05 Ω cm2 at 800 °C have been prepared.