(19,24,25,27−31) These degradation phenomena were reported for cells using yttria-stabilized zirconia (YSZ) and La 1– xSr xMnO 3−δ (LSM) or La 1– xSr xCo yFe 1– yO 3−δ (LSCF), which are the most common SOEC materials for the electrolyte and the oxygen electrode, respectively.
WHICH SCIENTIST PERFORMED THE CATHODE RAY EXPERIMENT CRACK
Postoperation analyses revealed pore and crack formation in the electrolyte material (23,24) or at the anode/electrolyte interface (22,25,26) as well as delamination of the anode from the electrolyte or the barrier layer. Particularly, microstructural and morphological changes at the oxygen electrode (anode) side occurring under electrolysis operation (i.e., anodic polarization) are a common problem, leading to severe performance deterioration. (16−23) Although the materials used in SOECs are similar to those in SOFCs, degradation phenomena can be quite different because of inverse operating conditions. Nevertheless, SOECs need to overcome obstacles concerning performance degradation and stability of stack and cell components. (9,13) Moreover, SOECs can be used for low-emission production of syngas or CH 4 via carbon capture from fossil-fuel-fired plants and coelectrolysis of water steam and carbon dioxide. (8−11) Combined with solid oxide fuel cells (SOFCs), high round trip system efficiencies up to about 44% can be achieved (assuming 10% energy loss by compressing hydrogen for storage purposes (12)). (1−3,5−7) Especially, solid oxide electrolysis cells (SOECs) may have a significant impact for both storage and sector coupling because of their potential for highly efficient production of hydrogen. (1−5) Therefore, sector coupling as well as energy-storage systems may play an important role in the future energy supply, and hydrogen technologies could become a key solution in both of these areas. However, these technologies suffer from problems in matching supply and demand as their energy production fluctuates on a daily, weekly, and seasonal basis, which is why they are also referred to as variable or intermittent renewable energy sources. This change will certainly include a high share of renewable electricity production from wind and solar power. The energy sector has to face drastic changes if the ever-growing global demand for energy shall be met with zero- or low-emission technologies. Such measurements can thus detect and quantify the buildup of high internal gas pressures in closed pores at the anode side of solid oxide electrolysis cells. Hence, we conclude that the formation of highly pressurized oxygen (up to gas pressures of ∼10 4 bar) in closed pores is responsible for this strong capacitive effect at anodic overpotentials. We demonstrate that this huge capacitance increase agrees very well with calculated chemical capacitances deduced from a real gas equation. While the chemical capacitance of dense and porous electrodes decreased as expected with increasing anodic overpotential, electrodes with closed pores exhibited very unusual peaks with extremely high values of >8000 F/cm 3 at overpotentials of >100 mV. Chemical capacitance values of the electrodes were derived from the obtained spectra. Electrochemical impedance spectroscopy (EIS) was performed in synthetic air at 460 and 608 ☌ with anodic DC voltages up to 440 mV. Furthermore, electrodes with closed porosity were fabricated by depositing a dense capping layer on a porous film.
Dense and porous electrodes (open porosity) were prepared by using different parameters during pulsed laser deposition (PLD). The chemical capacitance of La 0.6Sr 0.4CoO 3−δ (LSC) thin film microelectrodes with different microstructures was investigated upon varying anodic DC voltages.
0 kommentar(er)
