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

Abstract

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.