Intermediate Temperature Solid Fuel Cells Research Articles

Electrochemical Property Assessment of Pr2CuO4 Submicrofiber Cathode for Intermediate-Temperature Solid Oxide Fuel Cells

The Pr2CuO4 (PCO) submicrofiber precursors are prepared by electrospinning technique and the thermo-decomposition procedures are characterized by thermal gravity (TG), X-ray diffraction (XRD), Fourier transform infrared spectoscopy (FT-IR), and scanning electron microscopy (SEM), respectively. The fibrous PCO material was formed by sintering the precursors at 900 °C for 5 hrs. The highly porous PCO submicrofiber cathode forms good contact with the Ce0.9Gd0.1O1.95 (CGO) electrolyte after heat-treated at 900 °C for 2 hrs. The performance of PCO submicrofiber cathode is comparably studied with the powder counterpart at various temperatures. The porous microstructure of the submicrofiber cathode effectively increases the three-phase boundary (TPB), which promotes the surface oxygen diffusion and/or adsorption process on the cathode. The PCO submicrofiber cathode exhibits an area specific resistance (ASR) of 0.38 Ω cm2 at 700 °C in air, which is 30% less than the PCO powder cathode. The charge transfer process is the rate limiting step of the oxygen reduction reaction (ORR) on the submicrofiber cathode. The maximum power densities of the electrolyte-support single cell PCO|CGO|NiO-CGO reach 149 and 74.5 mW cm−2 at 800 and 700 °C, respectively. The preliminary results indicate that the PCO submicrofiber can be considered as potential cathode for intermediate temperature solid fuel cells (IT-SOFCs).

NdBaCu2O5+δ and NdBa0.5Sr0.5Cu2O5+δ layered perovskite oxides as cathode materials for IT-SOFCs

Cobalt-free perovskite oxides NdBaCu2O5+δ (NBCO) and NdBa0.5Sr0.5Cu2O5+δ (NBSCO) has been investigated as cathode materials in intermediate-temperature solid fuel cells (IT-SOFCs). The crystal structure, thermal expansion, electrical conductivity and electrochemical properties have been characterized by X-ray diffraction (XRD), dilatometer, four-probe dc method, electrochemical impedance spectroscopy (EIS) and cathodic polarization examinations. The average thermal expansion coefficients (TEC) values of NBCO and NBSCO are 13.0 × 10−6/°C and 14.5 × 10−6/°C, which are more desirable on combining with the electrolytes than cobalt-based cathodes. The partly substitution of Sr on B-site increases the electron hole concentration and improves the conductivity. The polarization resistances values of NBSCO are 0.205 Ωcm2, 0.200 Ωcm2 and 0.135 Ωcm2, whereas the polarization resistances values of NBCO are 8.61 Ωcm2, 3.18 Ωcm2 and 0.83 Ωcm2 at 600 °C, 700 °C and 800 °C, respectively. The improved electrochemical performance of NBSCO should be ascribed to the higher conductivity as well as the improved oxygen adsorption/desorption and oxygen ions diffusion processes.

SmBa 0.5Sr 0.5Cu 2O 5+ δ and SmBa 0.5Sr 0.5CuFeO 5+ δ layered perovskite oxides as cathodes for IT-SOFCs

Novel Cobalt-free layered perovskite oxides SmBa 0.5Sr 0.5Cu 2O 5+ δ (SBSCO) and SmBa 0.5Sr 0.5CuFeO 5+ δ (SBSCFO) were investigated as cathode materials for intermediate-temperature solid fuel cells (IT-SOFCs). The thermal expansion coefficients (TEC) of SBSCO and SBSCFO were 14.1 × 10 −6/°C and 14.9 × 10 −6/°C in 50 °C–800 °C, which were more compatible with electrolyte than cobalt-based cathodes. When A′-site is partially substituted by Sr, the conductivity of SBSCO and SBSCFO had been improved. The max electrical conductivity of SBSCO was 277.7 S cm −1, about one order of magnitude higher than SmBaCu 2O 5+ δ . Polarization resistance of SBSCO is 0.25 Ω cm 2 at 650 °C, which is twice lower than that of SmBaCu 2O 5+ δ (SBCO). This implies SBSCO has higher activity for oxygen reduction than SBCO. Preliminary results indicate that SBSCO are promising as cathodes for IT-SOFCs.