Ceria based electrolyte materials have shown potential application in low temperature solid oxide fuel cells (LT-SOFCs). In this paper, Sm3+ and Nd3+ co-doped CeO2 (SNDC) and pure CeO2 are synthesized via glycine-nitrate process (GNP) and the electro-chemical properties of the nanocrystalline structure electrolyte are investigated using complementary techniques. The result shows that Sm3+ and Nd3+ have been successfully doped into CeO2 lattice, and has the same cubic fluorite structure before, and after, doping. Sm3+ and Nd3+ co-doped causes the lattice distortion of CeO2 and generates more oxygen vacancies, which results in high ionic conductivity. The fuel cells with the nanocrystalline structure SNDC and CeO2 electrolytes have exhibited excellent electrochemical performances. At 450, 500 and 550 °C, the fuel cell for SNDC can achieve an extraordinary peak power densities of 406.25, 634.38, and 1070.31 mW·cm−2, which is, on average, about 1.26 times higher than those (309.38, 562.50 and 804.69 mW·cm−2) for pure CeO2 electrolyte. The outstanding performance of SNDC cell is closely related to the high ionic conductivity of SNDC electrolyte. Moreover, the encouraging findings suggest that the SNDC can be as potential candidate in LT-SOFCs application.

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Heterostructure technologies have been regarded as promising methods in the development of electrolytes with high ionic conductivity for low-temperature solid oxide fuel cells (LT-SOFCs). Here, a novel semiconductor/insulator (n–i) heterostructure strategy has been proposed to develop composite electrolytes for LT-SOFCs based on CeO2 and the insulator amorphous alumina (a-Al2O3). The constructed CeO2/a-Al2O3 electrolyte exhibits an ionic conductivity of up to 0.127 S cm–1, and its fuel cell achieves a maximum power density (MPD) of 1017 mW cm–2 with an open-circuit voltage (OCV) of 1.14 V at 550 °C without the short-circuiting problem, suggesting that the introduction of a-Al2O3 can effectively suppress the electron conduction of CeO2. It is found that the potential energy barrier at the heterointerfaces caused by the ultrawide band gap of the insulator a-Al2O3 plays an important role in restraining electron conduction. Simultaneously, the thermoelectric effect of the insulator induces more oxygen vacancies because of interface charge compensation, which further promotes ionic transport and results in high ionic conductivity and fuel cell performance. This study presents a practical n–i heterostructure electrolyte design, and further research confirmed the advanced functionality of the CeO2/a-Al2O3 electrolyte. Our study may open frontiers in the field of developing high-efficiency electrolytes of LT-SOFCs using insulating materials such as amorphous alumina.

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This study systematically investigated the effects of a single B-site dopant (Fe, x = 0–1.0) on the structure and oxygen reduction reaction of the Ba0.9K0.1CoO3−δ (BKC) material used as a cathode for low-temperature solid oxide fuel cells (LT-SOFCs). The structural, electronic, and electrocatalytic properties of the cathode materials prepared by a sol–gel method were comparatively characterized. The results indicated that cubic perovskite structure BKF x C (Fe, x = 0.5, 0.6) materials had been formed by calcination at 900 °C for 5 h. Moreover, in order to examine the electrochemical properties of BKF x C, the BKF x C cathode was constructed on the Sm0.075Nd0.075Ce0.85O2−δ (SNDC) electrolyte (BKFC/SNDC/BKFC: denoted as symmetric cells); the lowest polarization resistance (R P) was obtained for the BKF0.5C symmetric cell (1.6 Ω·cm2 at 550 °C), which demonstrated much higher electrocatalytic activity than that of a similar cell with the BKF0.6C cathode (2.87 Ω·cm2 at 550 °C). A single cell with the BKF0.5C cathode achieved a top power density of 752 mW·cm–2 at 550 °C, which is 0.35 times higher than that of the single cell with the BKF0.6C cathode (power density: 556 mW·cm–2). The corresponding total interface R P of the fuel cell was 0.303 Ω·cm2, lower than that of the doping amount of 0.6 (550 °C, 0.402 Ω·cm2). Meanwhile, O2 temperature-programmed desorption (O2-TPD) and thermogravimetric (TG) analysis were used to characterize the valence of Fe and Co changing from +4 to +3 as well as the stable structure of the material from room temperature to 600/1000 °C. As a result, a highly efficient method for the innovative BKFC cathode was developed in this work.