Electronic Structural Optimization of the Air Electrodes for Reversible Protonic Ceramic Electrochemical Cells via IIIA Cation Doping

Reversible protonic ceramic electrochemical cells (R-PCECs) have emerged as a novel technology for clean and efficient energy generation and storage. Improving the oxygen and proton conduction characteristics and stability of air electrodes at intermediate temperatures is crucial for achieving a high performance. Herein, we optimize the electronic structure of a state-of-the-art PrBa0.8Ca0.2Co2O5+δ (PBCC) air electrode via doping IIIA cations (Al3+, Ga3+, and In3+). It is shown that PrBa0.8Ca0.2Co1.9Ga0.10O5+δ (PBCCGa0.10) exhibits improved oxygen reaction activity and hydration capability. Density functional theory calculations confirm that Ga doping provides the most favorable electronic structure. An R-PCEC with PBCCGa0.10 achieves a peak power density of 2.21 W cm–2 and a current density of −4.64 A cm–2 at 1.3 V at 650 °C. Additionally, the PBCCGa0.10 electrode performs good operational stability in FC mode (for about 100 h), EC mode (for about 100 h), and reversible cyclic testing (over 200 h) at 600 °C.