Researchers' interest in proton-conducting reversible solid oxide cells (RSOCs) is growing due to their distinct benefits. In the present work, single-phase BaCe0.9–xMoxY0.1O3–δ (x = 0, 0.025, 0.05, 0.1, 0.2) electrolyte is prepared via sol-gel method and sintered at 1400 °C for 10 h. Optimal density, structure, composition, electrochemical performance, and thermal stability are confirmed via SEM, XRD, EDS, XPS, FTIR, EIS, and TGA/DSC. The conductivity of the grain interior and boundaries between 127 and 727 °C is reported for the first time in SOFC studies. The BaCe0·875Mo0·025Y0·1O3–δ sample shows a grain interior conductivity of 1.3 × 10−3 S cm−1 at 707 °C with grain interior activation energy of 0.75 eV (127–727 °C), and a grain boundary activation energy of 0.85 eV (380–727 °C), 0.43 eV (167–357 °C) in air atmosphere, respectively. BaCe0.875Mo0.025Y0.1O3–δ showed extreme stability for 300 h, and thus can be considered suitable for an efficient protonic conductor at intermediate temperatures.