Objective
- INCREASE OF EFFICIENCY BY DECREASING CHEMIC POLARIZATION LOSSES
- HIGHER ENERGY PRODUCTION RATE, INCREASE OF POWER OUTPUT
- REDUCTION OF OPERATING TEMPERATURE, INCREASE OF CELL VOLTAGE.
An alumina supported air electrode of La0.85Sr0.15MnO3 (SLM) was developed on which a 8 um layer of Y2O3 stabilised zirconia (YSZ) was deposited by electrochemical vapour deposition (ECVD). The alumina support was made by tape casting, and the 15SLM powder was obtained using a citrate pyrolysis technique. The final composite was made by tape casting 15SLM on the sintered alumina structure followed by sintering of the composite at 1100 C in air for 10 hours. The alumina support was 1 mm thick with a porosity of 45% and a mean pore size of about 10 um. The cathode had a thickness of 10-35 um, a porosity of 60-70% and a mean pore size of 0.4 um. Sintering characteristics and the electrical conductivity of SLM as a function of strontium content were investigated.
15SLM was directly tape cast on sintered tapes of 3YSZ. The resulting half cells, with a cathode/electrolyte active area of 3 cm{2}, were combined with a platinum paste anode and used for cell testing experiments. Satisfactory results were obtained. The voltage at open circuit was 1.13 V, and at 200 mA/cm{2} it was 0.55 V. Operating temperature was 1000 C, the fuel was hydrogen and the oxidant was air.
In addition to the deposition of the 8 um layer of YSZ, an intermediate membrane between the air electrode and the ECVD electrolyte was deposited. This 2.5 um thick membrane of 8YSZ was deposited by film coating and prevents the growth of zirconia in the air electrode during electrolyte deposition.
Leakage of hydrogen gas across the electrolyte and along the sealing edges of the cell causes erroneous open circuit voltages and no current in cells with ECVD electrolytes and platinum paste anodes.
Reactivity experiments between the cathode and thin electrolyte material have shown that reaction kinetics strongly control the reaction. For tape cast YSZ with SLM air electrodes, only diffusion of lanthanum or strontium into YSZ was observed at relatively high temperatures (1100-1150 C) whereas powder mixture s of the same materials at these temperatures yielded La2Zr2O7 or SrZr03. For alumina supported air electrodes with ECVD electrolyte, alumina reacted with 15SLM at these temperatures. At lower temperatures (850 C or 1000 C) no reaction products could be observed between 15SLM and YSZ in the latter composites. Reactivity experiments between alumina supported ECVD electrolytes (YSZ) and nickel(II) oxide have shown that nickel is able to diffuse through the electrolyte layer into alumina at temperatures of 1100 C or 1150 C. No nickel diffusion into tape cast YSZ electrolytes was observed.
DEVELOPMENT OF FABRICATION TECHNIQUE FOR MEMBRANES AND THIN LAYERS TO BE APPLIED IN SOFC TECHNOLOGY WITH THE AIM TO IMPROVE EFFICIENCY AND TO REDUCE POLARIZATION LOSSES. THE ACTIVITIES WILL BE CARRIED OUT BY ECN AND UNIVERSITY TWENTE IN CLOSE COOPERATION.
Fields of science
- engineering and technologymaterials engineeringcomposites
- natural scienceschemical sciencesinorganic chemistrytransition metals
- natural scienceschemical sciencesinorganic chemistryalkaline earth metals
- engineering and technologymaterials engineeringcoating and films
- engineering and technologyenvironmental engineeringenergy and fuels
Programme(s)
Topic(s)
Data not availableCall for proposal
Data not availableFunding Scheme
CSC - Cost-sharing contractsCoordinator
PETTEN
Netherlands