Assessment of the Y-doped Ca3Co4O9 thorn d as cathode material for proton-conducting fuel cells

This work presents the investigation of functional properties of the yttrium-doped Ca3 Co4O9+3 complex oxides as the prospective cathode materials for the proton-conducting fuel cells. The phase equilibria in the 1/2Y2O3-CaO-1/3Co3O4 system at 900 & DEG;C in air is experimentally observed, and the phase diagram is constructed. The misfit-layered structure of the Ca3-kYkCo4O9+3 solid solutions, and their chemical compatibility in air with proton-conducting electrolytes BaCe0.7 Ba3Ca1.18Nb1.82O8.73 are established. Functional properties of the obtained Ca3-kYkCo4O9+3 materials have been studied. The oxygen nonstoichiometry values of 3 at room temperature are equal to 0.48 and 0.62 for Ca2.5Y0.5Co4-O9+3 and Ca2YCo4O9+3, respectively. The electrical conductivity in air reaches maximum value of 32 S cm-1 at 800 & DEG;C for Ca2.5Y0.5Co4O9+3. The values of linear thermal expansion coefficient for Ca2.5Y0.5Co4O9+3 and Ca2YCo4O9+3 are equal to 13.5 x 10-6 and 14 x 10-6 K-1 in the temperature range of 25-800 & DEG;C in air. Minimum value of the polarization resistance Rp of 0.86 U cm2 at 600 & DEG;C is observed for the Ca2YCo4O9+3 electrode on the BaCe0.7Zr0.1-Y0.1Yb0.1O3-3 substrate. Results of the work demonstrate that Y-doping of Ca3Co4O9+3 can be recommended as the successful strategy for the enhancement of the electrochemical performance of the cathodes, based on Ca3Co4O9 thorn s, in the solid oxide fuel cells with the proton-conducting electrolytes.& COPY; 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.