B‐Site Multi‐Element Micro‐Doping Engineered Air Electrodes With Fast Oxygen Kinetics for Reversible Protonic Ceramic Electrochemical Cells

ABSTRACT

Reversible protonic ceramic electrochemical cells (R‐PCECs) provide a promising route for integrated power generation and hydrogen production, yet their practical operation and commercialization remain constrained by sluggish and stability‐sensitive air electrode reactions at intermediate temperatures. Here, we employ a multi‐element micro‐doping strategy for designing layered double perovskite air electrodes with controlled Mo contents, namely PrBa _0.5 Sr _0.5 Co _1.5 Fe _0.29 Mn _0.1 Ni _0.1 Mo _0.01 O _5+δ (PBSCFMNM01) and PrBa _0.5 Sr _0.5 Co _1.5 Fe _0.27 Mn _0.1 Ni _0.1 Mo _0.03 O _5+δ (PBSCFMNM03). The unique composition of the B‐site promotes defect tolerance, high oxygen vacancy concentration, and rapid surface exchange kinetics, while at the same time ensuring exceptional phase stability under harsh environmental conditions. Furthermore, PBSCFMNM03, with its higher Mo content, exhibits enhanced oxygen‐vacancy‐related surface oxygen species, stronger hydration behavior, faster oxygen reduction reaction (ORR) kinetics, and reduced polarization resistance. When incorporated as the air electrode in R‐PCECs, PBSCFMNM03 delivers improved fuel cell performance (1.10 W cm ⁻² ) and enhanced electrolysis performance (1.88 A cm ⁻² at 1.3 V) at 650°C, with stable long‐term reversible operation and superior performance below 550°C. These results identify PBSCFMNM03 as an efficient air electrode for R‐PCECs and establish a multi‐element micro‐doping strategy as valuable guidance for designing air electrodes for R‐PCECs.