Controlled growth of Pr_1.5Ba_1.5Cu₃O₇ cubes to meliorate the cathode reaction for protonic ceramic fuel cells

Efforts to improve the performance of protonic ceramic fuel cells (PCFCs) have been hampered by the limited availability of cathode materials with high activity and durability. One potential approach to enhance electrocatalytic performance is by modifying the particle morphology of the cathode, which potentially reforms transport properties and active reaction sites. Herein, the configuration of cathode particles via controllable growth of cubes was used to ameliorate perovskite-related Pr_1.5Ba_1.5Cu₃O₇ (PBC). The PBC particle geometry changes to a cube when the calcination temperature is switched from 900 to 950 °C, exposing the {100} crystal facets on the surface. This gives rise to more surface oxygen vacancies and efficient Cu²⁺–O–Cu³⁺ electron hopping transition paths, favoring high electrocatalytic activity with expeditious oxygen adsorption/activation and facilitating the oxygen reduction reaction (ORR) process. The particle-cubic PBC cathode assembled at 950 °C (PBC-950) exhibited significantly enhanced performance, with a power output of 1982 mW·cm⁻² and a polarization resistance (R_P) of 0.028 Ω·cm² at 700 °C on a PCFC, outperforming other Co-based and Cu-based single-phase cathodes reported in the literature. Overall, the superior power and polarization performance, along with excellent durability over 200 h, suggest that PBC-950 is a promising alternative for PCFC cathodes. This study demonstrates the potential of controlling particle growth to design highly active electrodes with specialized properties, opening new avenues for material design in PCFCs and related electrocatalytic fields.