Synergistic Bulk and Surface Engineering for Expeditious and Durable Reversible Protonic Ceramic Electrochemical Cells Air Electrode

Abstract Reversible protonic ceramic electrochemical cells (R‐PCECs) offer the potential for high‐efficiency power generation and green hydrogen production at intermediate temperatures. However, the commercial viability of R‐PCECs is hampered by the sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) within conventional air electrodes operating at reduced temperatures. To address this challenge, this work introduces a novel approach based on the simultaneous optimization of bulk‐phase metal‐oxygen bonds and in‐situ formation of a metal oxide nano‐catalyst surface modification. This strategy is designed to expedite the ORR/OER electrocatalytic activity of air electrodes exhibiting triple (O²⁻, H⁺, e⁻) conductivity. Specifically, this engineered air electrode nanocomposite‐Ba(Co_0.4Fe_0.4Zr_0.1Y_0.1)_0.95Ni_0.05F_0.1O_2.9‐δ demonstrates remarkable ORR/OER catalytic activity and exceptional durability in R‐PCECs. This is evidenced by significantly improved peak power density from 626 to 996 mW cm⁻² and highly stable reversibility over a 100‐h cycling period. This research offers a rational design strategy to achieve high‐performance R‐PCEC air electrodes with superior operational activity and stability for efficient and sustainable energy conversion and storage.