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Solid Oxide Fuel Cells (SOFCs) have suitable perspectives to replace their classical counterparts for the distributed generation of electrical energy with small and medium power sources (50 kWel). The main advantages of SOFCs rely on the high conversion efficiency and low environmental impact. Practical SOFC operating temperatures between 600 ◦C and 800 ◦C are aimed to increase life-time and reduce costs. These can be achieved only by using electrolytes with proper ionic conductivity at intermediate temperatures. This review deals with a survey of the current research on advanced materials to be used as electrolyte for intermediate or low temperature solid oxide fuel cells. Specific properties such as reaction mechanism, chemical compatibility, effects of dopants, and conductivity are discussed.

A composite Ni-La-Ce0.8Gd0.2O2 catalyst was investigated for the autothermal reforming of propane. A stable performance was recorded during a 100 h endurance test with a syngas yield of 85% at 800 °C. The catalyst was also investigated as anode for the direct utilization of propane in solid oxide fuel cells (SOFCs). This catalyst appeared less affected by carbon deposition during SOFC operation than conventional Ni-cermets. Schematic illustration of a SOFC operating with direct utilization of propane .

A composite Ni–perovskite anode was investigated for operation in dry propane-fed intermediate temperature solid oxide fuel cells (IT-SOFC). A La 0.6 Sr 0.4 Fe 0.8 Co 0.2 O 3 (LSFCO) perovskite, characterized by mixed electronic–ionic conductivity, was used to support a highly dispersed Ni-phase. However, the catalyst structure was modified during SOFC operation. X-ray diffraction analysis of the electrocatalyst showed that, after operation, Ni was mainly present as La 2 NiO 4 ; whereas, the LSFCO structure was partially modified into a lanthanum-depleted SrFe 1− x Co x O 3− y (SFCO) perovskite structure. These results were corroborated by X-ray photoelectron spectroscopy (XPS). Transmission electron microscopy (TEM) analysis showed the presence of a suitable dispersion of a nanosized Ni-phase and a strong interaction of Ni-enriched particles with the perovskite substrate. High reaction rates for the propane reaction were achieved with this electrocatalyst while minimizing carbon deposition. Power densities of about 300 mW cm −2 for dry propane oxidation were obtained at 800 °C in the presence of a thick gadolinia-doped ceria electrolyte. Fuel cell time-tests indicated promising electrochemical stability.

Ni-doped perovskite anodes have been investigated for oxidation of hydrogen in IT-SOFC. Perovskite materials are characterized by mixed electronic–ionic conductivity that combined to the high intrinsic catalytic activity of Ni allows to achieve high reaction rates. Suitable power densities of about 420 mW / cm 2 for the direct oxidation of hydrogen were achieved at 800 °C. Temperature programmed reduction analysis carried out in hydrogen reveals that the catalyst at 800 °C has totally lost the perovskite structure showing formation of substructures such as NiOOH and NiLa 2 O 4 .

In the present work, an electrochemically driven ceramic oxygen generator (ECOG) device is investigated. The present device is based on an electrode supported architecture. Structural and electrochemical characterizations of the electrochemical cell have been carried out. The O2 production rate has been measured showing a performance four times higher than the generally accepted targets for practical applications. The high performance obtained with this device, indicates that there are good perspectives to decrease the O2 production costs significantly decreased as well as small and light weight devices for portable uses are envisaged.

Gd-doped ceria (Ce0.80Gd0.20O1.90) obtained by several nanopowder synthesis processes are compared structurally, morphologically and electrochemically. The powders have been sintered into pellets and investigated by ac-impedance measurements. The electrochemical properties of the electrolytes have been correlated to the structural morphology of the sintered pellets. When the intergrain region exhibits an elevated interdiffusion, the observation of the grain boundaries becomes difficult while the electrochemical properties are improved. Acrylamide polymerization and oxalic co-precipitation techniques showed the best properties.

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A new alternating block copolymer was synthesized from dihydroxy-terminated poly-(ether ketone sulfone) and bis(dimethylamino)-terminated polydimethylsiloxane oligomers. The chemistry and the thermal properties are discussed. Surface chemical composition of films was analyzed by ESCA. Quantitative calculations showed a noticeable siloxane enrichment at the surface.

Composite cathodes have been investigated for operation in ceria-based electrolyte cells for operation at intermediate temperatures. Composites based on LSCFO/CGO and LSMO/CGO were studied. LSCFO-based oxides were found to be the best candidates giving the lowest cathodic overpotential. Structural morphology and electrochemical properties are discussed. An air separation electrochemical device based on AV driving force was constructed using LSCFO material. The device based on an electrode-supported architecture showed 1 Acm -2 at 0.15 V at the operational temperature of 800°C. Furthermore, the O 2 production was measured directly showing a flow rate of 3.5 ml min -1 cm -1 which is about four times higher than the minimum value acceptable for practical applications. The high electrochemical performance of the present device indicates good opportunities to significantly decrease the O 2 production costs as well as to produce small and light weight portable devices.

A fuel cell anode consisting of NiCu alloy and gadolinia doped ceria cermet has been investigated for CH 4 electro-oxidation. The effect of temperature and potential has been analysed. Impedance spectroscopy measurements have been carried out at different cell potentials. The operating voltage affected both ohmic and polarization resistances. These effects have been attributed to modifications of the anode surface chemistry. The polarization curves obtained in the temperature range from 650°C to 800°C showed the best cell performance at 800°C. Finally, the exhaust gases from the anode compartment were analysed by gas chromatography. No significant carbon deposition was observed after prolonged operation at 750°C in the presence of a humidified stream.