In Situ Exsolved Fe-Ni Nanocatalysts Enable High-Performance Anodes for Direct Methane Protonic Ceramic Fuel Cells.

Protonic ceramic fuel cells (PCFCs) directly fueled by methane offer a promising route for intermediate-temperature energy conversion. However, their practical development is severely constrained by sluggish reforming kinetics, severe carbon deposition, and high interfacial resistance. This arises from the inherent instability of conventional Ni-based anodes and mismatched electrode-electrolyte interfaces. To address these coupled challenges, we propose a catalytic interface reconstruction strategy that integrates a La-Ce-based electrolyte capable of low-temperature densification with a Ba-Zr-Ce-Fe-Nb-Y-Ni perovskite anode functional layer designed for in situ Fe-Ni alloy exsolution. The reduction-triggered exsolution of strongly anchored FeNi3 nanocatalysts not only dramatically accelerates methane activation and steam reforming but also ensures robust carbon tolerance by suppressing coke formation. The optimized La-Ce-based electrolyte enables dense membrane fabrication at reduced sintering temperatures, which consolidates the electrode-electrolyte interface. The assembled single cell achieves peak power densities of 758.44 mW·cm-2 (H2) and 614.18 mW·cm-2 (CH4, S/C = 2) at 650 °C, with a 39% reduction in polarization resistance compared to the catalyst-free counterpart under methane conditions. Detailed analysis reveals a critical shift in the rate-determining step from surface chemical limitation to charge transfer control, driven by strengthened reaction-diffusion coupling. This study demonstrates that coordinating electrolyte densification with catalytic exsolution provides a robust framework for developing high-performance, carbon-tolerant PCFCs for direct hydrocarbon conversion.