Abstract: Developing high ionic conducting electrolytes is crucial for applying proton-conducting fuel cell (PCFCs) practically. The current study investigates the effect of alumina on the structural, morphological, electrical, and electrochemical properties of CeO₂. Lattice oxygen vacancies are induced in CeO₂ by a general doping concept that enables fast ionic conduction at low-temperature ranges (300–500°C) for PCFCs. Rietveld refinement of the X-ray diffraction (XRD) patterns established the pure cubic fluorite structure of Al-doped CeO₂ (ADC) samples and confirmed Al ions’ fruitful integration in the CeO₂ lattice. The electronic structure of the alumina-doped ceria of the materials (10ADC, 20ADC, and 30ADC) has been investigated. As a result, it was found that the best composition of 30ADC-based electrolytes induced maximum lattice oxygen vacancies. The corresponding PCFC exhibited a maximum power output of 923 mW/cm² at 500°C. Moreover, the investigation proves the proton-conducting ability of alumina-doped ceria-based fuel cells by using an oxide ion-blocking layer.