Investigating the Proton Conduction in Co–Nd Co-Doped Amorphous Alumina-Based Electrolyte for Ceramic Fuel Cell

Amorphous oxide electrolytes have emerged as promising candidates for low-temperature solid oxide fuel cells (LT-SOFCs) due to their defect-rich structures and isotropic conduction pathways. In this work, we investigate the proton conduction behavior of Co–Nd codoped amorphous alumina (CNA) synthesized via a sol–gel route. Structural analyses confirm the persistence of the amorphous phase at intermediate operating temperatures (300–500 °C). Electrochemical testing reveals that 10-CNA (Co0.1Nd0.1AlO) achieves a peak power density of 836.8 mW cm–2 at 500 °C, surpassing both 5-CNA (Co0.05Nd0.05AlO) and Nd-alumina. Impedance spectroscopy and distribution of relaxation times (DRT) analysis demonstrate that codoping with Co and Nd reduces bulk and polarization resistances, thereby enhancing proton transport. Complementary thermal and spectroscopic analyses support the role of oxygen vacancies in facilitating conduction. This study demonstrates that Co-Nd codoped amorphous alumina exhibits enhanced proton conductivity and fuel cell performance, thereby contributing to the fundamental understanding of amorphous electrolyte design for next-generation ceramic fuel cells.