Exploring the effects of divalent alkaline earth metals (Mg, Ca, Sr, Ba) doped Nd2Ce2O7 electrolyte for proton-conducting solid oxide fuel cells

In this study, alkaline earth metals (Mg, Ca, Sr, Ba) doped Nd2Ce2O7 powders are synthesized by the gel autocombustion method. The effects of alkaline earth metals doped Nd2Ce2O7 on the phase structure, chemical stability, microstructure, and electrical properties are evaluated by the X-ray diffraction, scanning electron microscopy, Raman spectroscopy and electrochemical testing. All electrolytes reveal a cubic fluorite structure with an Fm-3m space group and remain excellent chemical stability at different atmospheres. The grain size and density of ceramics increase significantly, and a large number of oxygen vacancies are created after alkaline earth metals incorporated into Nd2Ce2O7. Generally, the total conductivity is associated with the number of oxygen vacancies and microstructure of ceramics. The electrolyte of Nd(1.85)Mg(0.15)Ce2(O)7-delta exhibits the highest electrical conductivity of 0.923 x 10(-2) S cm(-1 )and 1.542 x 10(-2) S cm(-1) in dry air and wet 5% H-2-Ar atmosphere at 700 degrees C, respectively. Additionally, with alkaline earth metals doped Nd2Ce2O7 as electrolytes, the proton-conducting single cells have a better open circuit voltage and peak power density. The single cell based on Nd(1.85)Mg(0.15)Ce2(O)7-delta electrolyte can reach 0.890 V and 483 mW cm(-2) at 700 degrees C. This was observed to stay constant without extreme degradation after short-term testing.