Entropy-Modulated Oxide-Metal Catalyst Architectures for Direct Ammonia Protonic Ceramic Fuel Cells

Protonic ceramic fuel cells (PCFCs) operating on NH₃ present a promising carbon-free energy pathway, yet their performance is often constrained by limited catalytic activity and degradation of conventional Ni-based anodes. Here, we report a high-entropy perovskite catalyst, Sr₂Fe₁Mo_0.2Mn_0.2Cr_0.2Cu_0.2Ni_0.2O_6-δ (SFMMCCN), employed as an anode catalyst layer in direct ammonia-fed PCFCs. Upon reduction, SFMMCCN undergoes in situ exsolution of Ni-Fe-Cu alloy nanoparticles within a stable oxide matrix. This architecture provides synergistic enhancement of NH₃ adsorption and decomposition through the combined effects of abundant surface acid sites and catalytically active alloy interfaces. As a result, the SFMMCCN cell achieves a record peak power density of 2.04 W cm⁻² at 700 °C and demonstrates excellent operational stability for over 255 h at 600 °C under NH₃ fuel. Compared to a bare cell, it exhibits significantly reduced polarization resistance and effectively suppresses Ni coarsening. Density functional theory calculations reveal that the high-entropy oxide framework, together with the exsolved Ni-Fe-Cu alloy, lowers the energy barriers for NH₃ decomposition, thereby accelerating overall catalytic kinetics. These findings highlight entropy-controlled oxide-metal architectures as a powerful strategy to achieve both high performance and durability in NH₃-fueled electrochemical systems, offering a viable pathway toward scalable and efficient hydrogen-based power generation.