Evolution of PrBa0.5Sr0.5Co1.5Fe0.5O5+δ cathode/BaZr0.1Ce0.7Y0.1Yb0.1O3−δ electrolyte interface of protonic ceramic fuel cells

The cathode/electrolyte interface plays a crucial role in the electrochemical performance and long-term operation stability of protonic ceramic fuel cells (PCFCs). In this study, electrochemical polarization-induced evolution of the interface of PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ (PBSCF) cathode/BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3−δ (BZCYYb) electrolyte, and its effect on the electrochemical performance of the single cell, were investigated. The results show that the peak power density of the cell increases from 0.67 W cm −2  at 0 h to 0.94 W cm −2  at 40 h during electrochemical polarization, and then decreases to 0.89 W cm −2  at 100 h as a result of the competition between the reduced ohmic resistance ( R Ω ) and the increased polarization resistance ( R p ). The microstructure of the cathode/electrolyte interface under cathodic polarization is characterized by the segregated CeO 2 -based nanoparticles at the PBSCF/BZCYYb interface, which enhances the interfacial contact between PBSCF and BZCYYb, and improves the grain and grain boundary conductivities of BZCYYb. On the other hand, SrO and Fe 2 O 3 segregation occurs on PBSCF under electrochemical polarization conditions, which is detrimental to the surface exchange and charge transfer processes and reduces the catalytic activity of the electrode. This study demonstrates that cation diffusion and segregation in the PBSCF electrode and BZCYYb electrolyte greatly affect the performance and stability of the cell, and thus the fundamental understanding and control of the cathode/electrolyte interface evolution is critical for the development of PCFCs.