High Proton Conductivity in xCuO/(1‐x)CeO2 Electrolytes Induced by CuO Self‐Nucleation and Electron‐Ion Coupling

Abstract

Abstract Operating within the 300–500 °C range, low‐temperature solid oxide fuel cells (LT‐SOFCs) enable efficient and sustainable energy conversion, addressing the limitations of conventional high‐temperature SOFCs. However, achieving >0.1 S cm−1 ionic conductivity in electrolytes remains challenging. Here, a novel approach utilizing CuO self‐nucleation and electron‐ion (E‐I) coupling in xCuO/(1‐x) CeO2 (CCO) semiconductor ionic membranes (x = 0–0.4) is presented. At the optimal 0.2CuO/0.8CeO2 composition, ionic conductivity exceeds 0.15 S cm−1, driven by E‐I coupling at the CuO/CeO2 heterojunction. This coupling creates a built‐in electric field (BIEF) via interfacial charge transfer, facilitating ion transport by lowering the activation energy for ion migration. The dual‐conduction pathway enabled by E‐I coupling not only facilitates electronic transfer and ionic transport but also optimizes charge transfer kinetics, achieving exceptional power densities of 750–900 mW cm−2 at 500–550 °C and 78 mW cm−2 at 300 °C. Density functional theory (DFT) calculations further validate the role of Cu2+ and Ce4+ valence states in generating interfacial charge transfer and enhancing ionic mobility. This innovative approach positions CuO/CeO2 as a state‐of‐the‐art electrolyte, building the critical conductivity‐performance gap in LT‐SOFCs. This study pioneers LT‐SOFC innovation by leveraging E‐I coupling and electrode–electrolyte synergy, unlocking superior ion transport and practical applicability.

Keywords

• CuO/CeO2 heterostructures
• CuO self‐nucleation
• electron‐ion coupling
• heterojunction engineering
• semiconductor ionic membranes (SIMs)