Unveiling synergistic H+/O2−/e− transport in modular triple-phase composite air electrodes for efficient reversible protonic ceramic cells

Proposes a functional modularization strategy to fabricate BZCY-GDC-LCO electrodes. • Exhibits low polarization resistance (0.141 Ω·cm 2 ) with 216 h stable operation. • Single cell delivers 0.757 W·cm −2 (FC) and 1.182 A·cm −2 at 1.3 V (EC) at 650 °C. Efficient triple-conduction (H + /O 2− /e − ) is vital for high-performance reversible protonic ceramic cells (R-PCCs), yet the underlying transport mechanisms and their specific impacts on electrode kinetics remain elusive. In this work, we employ a “functional modularization” strategy to engineer a BaZr 0.1 Ce 0.7 Y 0.2 O 3−δ -Gd 0.1 Ce 0.9 O 1.95 -LaCoO 3 (BZCY-GDC-LCO) triple-phase composite air electrode using commercially available precursors. The synergistic effects and individual roles of the conducting species in optimizing electrochemical kinetics were systematically investigated. The optimized BZCY-GDC-LCO electrode (1:1:1 mass ratio) exhibits excellent chemical compatibility, high oxygen vacancy concentration, and a well-distributed triple-phase boundary. Consequently, it achieves a low polarization resistance of 0.141 Ω·cm 2 at 650 °C and demonstrates robust long-term stability over 216 h of operation. Single-cell tests deliver a peak power density of 0.757 W·cm −2 in fuel cell mode and a current density of 1.182 A·cm −2 at 1.3 V in electrolysis mode at 650 °C. Kinetic analysis reveals oxygen adsorption/dissociation as the rate-determining step, while excessive steam partial pressure inhibits oxygen transport via surface site passivation. This work provides a scalable design strategy for high-performance R-PCC air electrodes, demonstrating that superior performance and favorable techno-economic feasibility can be achieved using conventional materials. Download: Download high-res image (166KB) Download: Download full-size image