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Vacancy-Redox Coupling at Interface-Engineered Heterostructures Enhances Reversible Energy Conversion in Protonic
Shuanglin Zheng1, Yuqi Geng1, Subrina Islam2
1School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK, USA.
Abstract:
Achieving efficient and durable oxygen electrocatalysis in protonic ceramic cells (PCCs) demands precise control of defect chemistry and cation redox under steam. Here, we design a hierarchically engineered oxygen electrode comprising a three-dimensional, mesh-like PrNi0.7Co0.3O3-δ (PNC) scaffold conformally integrated with a vacancy-rich PrOx nanophase. This architecture extends the reactive zone while the PrOx-PNC interphase enables vacancy-mediated redox coupling between Pr and Co, buffering local oxygen chemical potential and stabilizing the defect landscape during reversible operation. The enhanced activity is attributed to vacancy-assisted steam activation and defect-mediated oxygen surface exchange and is consistent with interfacial modulation of metal-oxygen covalency within an O 2p band center framework. The electrode delivers 1.75 W cm- 2 in fuel-cell mode and 2.77 A cm- 2 at 1.3 V in electrolysis at 600°C, maintains >92% Faradaic efficiency, and shows minimal degradation over 200 h. Our results establish a general strategy for coupling hierarchical transport with chemically active, redox-buffered interphases to achieve both high kinetics and durability in protonic electrochemical systems.
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