Development of melt infiltrated gadolinium doped ceria-carbonate composite electrolytes for intermediate temperature solid oxide fuel cells

Abstract

Composite electrolyte of gadolinium doped ceria and lithium sodium carbonate ((LiNa)(2)CO3-GDC) showing enhanced stability and mechanical strength has been fabricated using melt infiltration technique and tested as solid oxide fuel cell (SOFC) electrolytes. Porous matrix of GDC is fabricated by sintering at 1450 degrees C and subsequently the prefabricated matrix is melt infiltrated with mixture of (LiNa)(2)CO3 (1: 1 wt ratio). Ionic conductivities of the electrolytes, current-voltage characteristics and impedance spectra of the electrolyte supported bilayers with hydrogen as fuel and air as oxidant are measured. Physical characteristics of the composite electrolytes analysed using X-ray diffraction, scanning electron microscope (SEM), energy dispersive spectroscope, fourier transform infrared spectroscope and thermal gravimetric analysis show spatial distribution of active interphases, where in pore filled with (LiNa)(2)CO3 melt into prefabricated GDC matrix. As carbonate phase completely fills the GDC matrix, the ionic conductivity of melt infiltrated 30 wt% (LiNa)(2)CO3-GDC composite electrolyte is comparable to that of the solid state synthesised electrolyte at 600 degrees C. The performance of melt infiltrated 30 wt% (LiNa)(2)CO3-GDC composite electrolyte (similar to 2 mm) is much better (223mWcm(-2) at 579mA cm(-2)) than that prepared by solid state method at 750 degrees C. The morphology, thermal analysis and electrochemical studies of melt infiltrated composite electrolytes reveal better cell performance due to well sintered stable structure. (c) 2018 Elsevier Ltd. All rights reserved.