Development of Pr_(2-x)Sr_xCuO_(4±δ) mixed ion-electron conducting system as cathode for intermediate temperature solid oxide fuel cell

摘要

Mixed ionic-electronic conducting oxides Pr2-xSrxCuO4 +/-delta (x = 0, 0.2, 0.4, 0.5 and 0.6) are synthesized by combusting mixed precursors (metal acetates) under microwave heating followed by microwave sintering at 1000 degrees C for 4 h. Each composition of Pr2-xSrxCuO4 +/-delta solid solutions crystalizes into tetragonal structure within one single phase across the compositional range 0 = x = 0.5. The T'-phase Pr2CuO4 +/-delta transforms to the T*-phase at x = 0.4. Crystallite size reduces from 801(9) to 728(6) nm with an increase in the Sr content. The maximum dc-conductivity (sigma(dc) = 63.1(2) S cm(-1) at 700 degrees C) and minimum activation energy (E-a = 0.118(3) eV, below pseudo-transition temperature 620 degrees C) in Pr1.6Sr0.4CuO4 +/-delta is ascribed to optimum concentration of extrinsic dissociated defects. The performance of electrochemical symmetrical cells (Pr2-xSrxCuO4 +/-delta/ Ce0.9Gd0.1O1.95/ Pr2-xSrxCuO4 +/-delta) prepared using inkjet printing is found to be superior than spin coated (cathode) symmetrical cells. Increase in oxygen ion conductivity and surface oxygen exchange reaction rate with increasing Sr dopant concentration improve overall electrochemical performance of cathode. Minimum electrode polarization resistances 0.30(7) Omega cm(2) and 0.21(3) Omega cm(2) (at 700 degrees C) are obtained for symmetrical cells of Pr1.6Sr0.4CuO4 +/-delta cathode using spin-coating and inkjet printing methods, respectively. Electrochemical impedance spectroscopy studies suggest that the charge transfer step is the rate-limiting step during oxygen reduction reaction. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.