Trade-off between oxygen reduction reaction activity and CO(2)stability in a cation doped Ba(0.9)Co(0.7)Fe(0.3)O(3-delta)perovskite cathode for solid oxide fuel cells

The excellent oxygen permeability of the perovskite BaCoO(3)and its applicability as a cathode in solid oxide fuel cells are hindered by stability issues of carbonate formation in the presence of CO2, which degrades its excellent oxygen surface-exchange kinetics during the oxygen reduction reaction (ORR) process. In this work, we present a new type of Ba0.9Co0.7Fe0.2M0.1O3-delta(M = Zr, Nb, Y) perovskite oxide with high CO(2)tolerance with respect to their original compound Ba0.9Co0.7Fe0.3O3-delta(B90CF) by doping cations at the B-site. These cathodes show low polarization resistances (R-p) of 0.0687, 0.0719, and 0.0853 omega cm(2)for Ba0.9Co0.7Fe0.2Y0.1O3-delta(B90CFY), Ba0.9Co0.7Fe0.2Zr0.1O3-delta(B90CFZr), and Ba0.9Co0.7Fe0.2Nb0.1O3-delta(B90CFNb) at 700 degrees C, respectively, which are comparable to B90CF (0.0655 omega cm(2)). Moreover, after exposure to air containing 1% CO(2)for 1500 min, the electrochemical impedance spectroscopy (EIS) test demonstrated the improved CO(2)tolerance for the B90CFM cathode with Zr (Nb, Y) doping, where theR(p)of B90CFZr only increased by 31%, similar to 1/10 of that for B90CF. Barium carbonate on the B90CFZr cathode was obviously suppressed compared to B90CF according to SEM combined with EDS, XRD and FT-TR analysis. Doping high-valence metals at the B site of the B90CFM perovskite may increase the acidity on the surface and metal-oxygen bond free energy ( ABE ), leading to enhanced resistance to CO2. The trade-off between electrocatalytic activity and stability enable B90CFZr to be a promising cathode material for low and medium temperature SOFCs.