Boosting electrochemical performance of Ho3+ and Sm3+ co-doped CeO2 intermediate-temperature solid oxide membrane fuel cells by NiO

In this study, Ho3+ and Sm3+ co-doped CeO2 (Ho0.1Sm0.1Ce0.8O2-α, HSDC) and HSDC-2 wt% NiO (HSDC-2NiO) were synthesized to investigate the influence of the addition of sintering additive and calcining temperature on the structures, morphologies and conductivities of the samples. The XRD patterns showed that the phase structures of 800-HSDC, 1350-HSDC, 1450-HSDC and 1450-HSDC-2NiO were all cubic fluorite CeO2 solid solution. The conductivities of the ceramic sheets increased significantly with the increase of the addition of NiO and sintering temperature. 1450-HSDC-2NiO had the highest conductivities of 4.6 × 10−2 S cm−1 and 7.6 × 10−2 S cm−1 at 700 °C and 750 °C, respectively. The anode-supported thin film fuel cell: NiO-HSDC | 1450-HSDC-2NiO|LSNFCN was fabricated using La0.6Sr0.3Ni0.1Fe0.8Co0.1Ni0.1O3-δ (LSNFCN) as the cathode by a slurry spin-coating method. LSNFCN exhibited a perovskite structure with a good single-phase property. The maximum output current densities (Cmax) were 663 mA cm−2 and 904 mA cm−2, and the corresponding power densities (Pmax) were 334 mW cm−2 and 431 mW cm−2 of the 1450-HSDC-2NiO membrane (15 μm) at 650 °C and 700 °C, respectively. The durability of the thin film fuel cell at 650 °C showed that the OCV was relatively stable with a slight increase in Pmax and a significant increase in Cmax corresponding to a good stability within the testing range of 0–10 h. However, Pmax and Cmax were about 82% and 92% of the highest values after 40 h testing, respectively. The fuel cell performance and durability could be further improved by adding a stable barrier layer.