An Active Oxygen Electrode for Proton‐Conducting Solid Oxide Electrolysis Cells with High Faradaic Efficiency

Abstract Addressing the challenges posed by inferior electrochemical performance at low temperatures and the uncertain Faradaic efficiency (FE) represents a pivotal undertaking in the development of high performance and efficient proton‐conducting solid oxide electrolysis cells (P‐SOECs). In this work, a novel oxygen electrode material BaCo 0.8 Zr 0.1 Zn 0.1 O 3‐δ (BCZZ) is first designed and synthesized. At 600 °C, P‐SOECs with BCZZ oxygen electrode achieve an electrolysis current density of 1.98 A cm −2 with an ≈90% FE at 1.3 V. Utilizing 1‐inch P‐SOECs as a reliable platform, the effect of extrinsic operating conditions (i.e., steam concentration, voltage, current density, and temperature) and intrinsic properties of P‐SOECs (i.e., electrolyte material and electrolyte thickness) on FE are further systemically investigated, both experimentally and theoretically.