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This paper examines the relative REDOX stability and conductivity of new Cr-doped perovskite materials (Sm0.95Ce0.05Fe1-xCrxO3-δ, x = 0–0.10) for potential use as anode materials and sensors for reducing gases at low temperatures. These perovskite materials were characterized by XRD, XPS and SEM. A reduction stability test revealed that these perovskites are stable at temperatures below 800°C under reducing conditions. The introduction of Cr in the lattice was found to be in the form of Cr+3and Cr+6. As a function of Cr content, the ratio of Cr+3/Cr+6was found to increase. The reduction treatment tended to decrease the concentration of lattice oxygen but the surface adsorbed oxygen was found to be higher in reduced samples as compared to fresh samples. This observation suggested that these materials have a tendency to recapture oxygen when exposed to air after the reduction treatment. The reduction treatment improved the electrical conductivity due to the formation of nanoparticles. The x = 0.03 perovskite has highest electrical conductivity under both air and reducing atmospheres and shows the greatest promise for use in sensor applications for reducing gases at low temperatures.

The newly developed Sm0.95Ce0.05Fe1-xCoxO3-δperovskites were assessed as sensors for reducing gases. The solid state sensors were prepared in the form of pellets. Sensors with larger particle size and reduced grain boundaries are obtained as the concentration of cobalt is increased. The sensor’s surface is enriched with Sm and Co, but the Sm concentration decreases with an increase in cobalt content. The introduction of cobalt in the perovskite lattice results in an increase in lattice oxygen and a decrease in surface adsorbed oxygen. The electrical conductivity responses toward H2, CO and CH4(1–5% v/v) were measured in air and at different temperatures. The cobalt doping has improved the response to such an extent that H2, CO and CH4can be detected at room temperature. Response and recovery time of these sensors are associated with surface chemical composition and surface morphology.

The poisoning behavior of hydrogen sulfide at the concentrations presented has the effect of lessening the amount of coke formation experienced at the anode site of the active Ni0.7Co0.3-YSZ cermet. Although the effect of coke formation becomes more dramatic and detrimental to the cell as the length of the hydrocarbon chain increases, the ability of the hydrogen sulfide to protect the anode against coke formation also increases, producing a smaller reduction in exchange current density with increasing hydrocarbon length. For the case of biodiesel fuel, at a concentration of 5 % hydrogen sulfide, the exchange current density is higher and the cell survives much longer than with pure biodiesel fuel. Hydrogen sulfide also has the effect of increasing the lifetime of the cell to be several times that of the pure hydrocarbon fuel.

The newly developed Sm0.95Ce0.05Fe1-xCoxO3-δ perovskites were assessed as sensors for reducing gases. The solid state sensors were prepared in the form of pellets. Sensors with larger particle size and reduced grain boundaries are obtained as the concentration of cobalt is increased. The sensor's surface is enriched with Sm and Co, but the Sm concentration decreases with an increase in cobalt content. The introduction of cobalt in the perovskite lattice results in an increase in lattice oxygen and a decrease in surface adsorbed oxygen. The electrical conductivity responses toward H2, CO and CH4 (1-5%v/v) were measured in air and at different temperatures. The cobalt doping has improved the response to such an extent that H2, CO and CH4 can be detected at room temperature. Response and recovery time of these sensors are associated with surface chemical composition and surface morphology