Article scientifique

An efficient hierarchical nanostructured Pr6O11 electrode for solid oxide fuel cells

J. Mater. Chem A (03/10/2020)
Rakesh K. Sharma, Elisabeth Djurado
This work reports the structural, microstructural, electrochemical properties and chemical stability of Pr6O11 for its promising use as IT- SOFC cathodes. Various hierarchical nanostructured Pr6O11 films on a GDC (Ce0.9Gd0.1O2−δ) substrate are successfully deposited by a low-temperature and low-cost electrostatic spray deposition (ESD) process on a GDC. Pr6O11 films crystallize in a fluorite cubic structure after calcination at 700 °C for 2 h in the air. Herein, different and innovative microstructures, such as thin, thick, dense, reticulated, coral and columnar-types, have been obtained by varying the ESD key process parameters such as nature of the solvent composition, deposition time, nozzle-to-substrate distance, flow rate, and the deposition temperature. Pure BC and addition of 33% vol. H2O, as well as ethanol to pure BC, give a columnar microstructure with a continuous, dense thin layer adjacent to the electrolyte. The electrochemical properties are found to be strongly dependent on the microstructure and architecture of the cathode films. Polarisation resistance values (Rpol) are decreased from 74.94 to 12.78 and then to 2.21 Ω cm2 by changing the microstructure from dense thin morphology to porous reticulated and then porous columnar microstructures, thanks to an improved number of specific surface area and TPB points. Moreover, the Rpol value of the columnar microstructure decreases down to 0.06 and 0.026 Ω cm2 at 500 °C and 600 °C, respectively, after improving the current collection by adding an LSCF SP layer on top of ESD layer. To the best of our knowledge, double layer Pr6O11 deposited by ESD and SP is characterized by the lowest Rpol value for any composition of the oxygen electrode. In addition, Pr6O11 does not show any reactivity with GDC over 10 days in air at 800 °C. A single cell made of a commercial (Ni-3YSZ/Ni-8YSZ/8YSZ/GDC) half cell and this double layer cathode delivers a preliminary maximum power density of 500 mW cm-2 at 700 °C which has to be optimized.