Surface decoration of Ba-enriched Fe-based air electrodes with Co-based catalysts for robust protonic ceramic electrochemical cells

Abstract

Protonic ceramic electrochemical cells (PCECs) are promising for renewable energy conversion, yet their commercialization is hindered by the limited durability and thermal expansion mismatch of commonly used Co-based air electrodes. Although Fe-based alternatives offer better thermal compatibility, they suffer from inferior oxygen reduction kinetics. Herein, we report a surface decoration strategy to address these challenges by decorating a Ba-enriched Ba_1.02FeO_3−δ (B_1.02F) scaffold with a Co-based catalyst coating. Electron microscopy and spectroscopic characterization confirm the formation of a composite surface coating comprising Co₃O₄ and in situ formed Ba–Co–O species. The resulting catalyst-coated B_1.02F electrode (B_1.02F-CC) effectively combines the thermomechanical robustness of the Fe-based backbone with the high catalytic activity of Co species. Electrochemical analyses reveal that the catalyst coating markedly accelerates both oxygen surface exchange and charge-transfer kinetics. Consequently, single cells based on the B_1.02F-CC electrode deliver a maximum power density of 1.46 W cm⁻² and sustain stable operation for 600 h at 650 °C. Additionally, the single cell maintains reliable performance for 17 thermal cycles (300–650 °C) with negligible degradation. This work validates a robust surface decoration strategy to reconcile the trade-off between electrocatalytic activity and thermomechanical stability, providing a viable pathway toward durable, high-performance air electrodes for PCECs.