Development of La0.63Ga0.37Nb0.74Fe0.26O3-δ Electrodes for Solid Oxide Fuel Cells Via Various Synthesis Routes

Abstract

In this study, La₀.₆₃Ga₀.₃₇Nb₀.₇₄Fe₀.₂₆O₃-δ electrodes developed through four different methods for use in solid oxide fuel cells operating at intermediate temperatures are systematically investigated in this study. Coprecipitation, sol gel, solid state, and hydrothermal synthesis were the techniques that were compared. The coprecipitation approach was shown to be the best synthesis route after thorough analysis, exhibiting superior structural and electrochemical features. In coprecipitated samples, Raman spectroscopy showed prominent Ga–O symmetric stretching at 532 cm⁻¹, La–O stretch at 400 cm⁻¹, and Fe–O modes at 656, 713 cm⁻¹. Nb–O vibration was observed at 882 cm⁻¹, with distinct vibrational modes suggesting increased crystallinity and oxygen vacancy generation. The material's phase features were validated by XRD analysis showing broadened peaks corresponding to nanocrystalline structure with 12.9 nm crystallite size, and reference phases confirmed by JCPDS 01-084-1020 (FeNbO₄) and 03-065-0945 (GaLaO₃-type). An ideal band gap of 1.44 eV was found by UV–Vis spectroscopy, indicating advantageous electronic characteristics. Electrochemical impedance spectroscopy revealed the lowest polarization resistance values of 4.1 Ω at 600°C and 3.1 Ω at 650°C, among all samples. Fuel cell testing showed that coprecipitated samples excelled sol gel at 0.890 V, solid state at 0.870 V, and hydrothermal at 0.843 V, reaching the highest open circuit voltage of 0.960 V at 650°C. The desirable structure, phase purity, and defect composition of coprecipitated electrodes are responsible for their exceptional performance. Offering considerable potential for developing sustainable energy conversion technologies, these results solidify coprecipitation as the preferred synthesis technique for high performance intermediate temperature solid oxide fuel cell electrodes. The goal of future studies should be to scale manufacturing while preserving these beneficial characteristics.