Effect of Nb and Y co-doping on the layered perovskite cathode of protonic ceramic fuel cells

To address the performance bottleneck of protonic ceramic fuel cells (PCFCs) associated with sluggish oxygen reduction reaction (ORR) kinetics, this study explores the co-doping effect of Nb and Y in layered perovskite oxides to develop an efficient and stable cathode. A series of PrBa_0.9Co_1.96Nb_xY_0.04-xO_5+δ (x = 0, 0.01, 0.02, 0.03, and 0.04) cathode materials were synthesized via a sol-gel method and systematically evaluated. Among them, the optimized cathode material PrBa_0.9Co_1.96Nb_0.01Y_0.03O_5+δ with x = 0.01 (PBCNb_0.01Y_0.03) demonstrates enhanced surface oxygen vacancy concentration, higher Co⁴⁺ content, and improved catalytic ORR activity. The PBCNb_0.01Y_0.03 cathode exhibits a reduced polarization resistance across 700–550 °C compared to its counterparts. Co-doping of Nb and Y optimizes the processes of charge transfer, oxygen adsorption/dissociation, and ion migration, as suggested by the distribution of relaxation time (DRT) analysis. A peak power density of 2.23 W cm⁻² is achieved at 700 °C from the single cell with PBCNb_0.01Y_0.03 cathode, outperforming most reported cathodes with similar architectures. Additionally, a promising electrochemical stability over extended operation (100 h) is demonstrated at 0.5 A cm⁻².