Low Temperature Fast Mixed OH⁻/H⁺ Ionic Conductor in Doped Strontium Cerates

The drawbacks of high temperature solid oxide fuel cells (HT‐SOFCs) prompt efforts to lower operating temperatures to near ambient temperatures (NAT). Here the high mixed OH − /H + ionic conductivity in doped SrCeO 3 below 100 °C is reported. The SrCe 0.8 Y 0.2 O 3− δ (SCYO20) electrolyte demonstrates a high ionic conductivity of 12 mS cm −1 in water and 9 mS cm −1 in wet air at 60 °C and an excellent long‐term stability over 100 h. Solid state nuclear magnetic resonance confirms the presence of protons and hydroxide ions in the hydrated oxides and their correlation with Y dopant. Demonstration of direct ammonia fuel cells using the SCYO20 electrolyte indicates the practical application value of this material. The OH − conduction of SrCe 0.7 Sn 0.2 Y 0.1 O 3− δ (SCSY721) is demonstrated by electrolysis of D 2 O. The introduction of KOH significantly increases the availability of OH − feed ions, leading to a remarkable improvement of ionic conductivity of SCSY721 electrolyte which is increased by 27 times, 56.34 mS cm −1 in 6 m KOH at 90 °C. The increased ionic conductivity due to the presence of high concentration of extrinsic conducting ions, here are OH − ions, is called as ‘feeding effect’. This study offers new electrolyte materials for cost‐effective, and durable electrochemical devices such as NAT‐SOFCs.