Oxygen electrodes are provided, comprising a perovskite compound having Formula (I), Sr(Ti.sub.1-xFe.sub.x-yCo.sub.y)O.sub.3-wherein 0.90x0.40 and 0.02y0.30. Electrochemical devices comprising such oxygen electrodes are also provided, comprising a counter electrode in electrical communication with the oxygen electrode, and a solid oxide electrolyte between the oxygen electrode and the counter electrode. Methods of using such electrochemical devices are also provided, comprising exposing the oxygen electrode to a fluid comprising O.sub.2 under conditions to induce the reaction O.sub.2+4e.sup..fwdarw.2O.sup.2, or to a fluid comprising O.sup.2 under conditions to induce the reaction 2O.sup.2.fwdarw.O.sub.2+4e.sup..

A supported catalyst for decomposing an organic substance that includes a support and a catalyst particle supported on the support. The catalyst particle contains a perovskite-type composite oxide represented by A.sub.xB.sub.yM.sub.zO.sub.w, where the A contains at least one selected from Ba and Sr, the B contains Zr, the M is at least one selected from Mn, Co, Ni and Fe, y+z=1, x0.995, z0.4, and w is a positive value satisfying electrical neutrality. A film thickness of a catalyst-supporting film supported on the support and containing the catalyst particle is 5 m or more, or a supported amount as determined by normalizing a mass of the catalyst particle supported on the support by a volume of the support is 45 g/L or more.

An oxygen evolution catalyst of the formula: Sr.sub.2MCoO.sub.5 where M=Al, Ga wherein M is bonded with four oxygen atoms to form a tetrahedron. The catalyst is operated at a potential of less than 1.58 volts vs. RHE at a current density of 50 A/cm.sup.2 for a pH of 7-13. The catalyst is operated at a potential of less than 1.55 volts vs. RHE at a current density of 50 A/cm.sup.2 and a pH of 13. The oxygen evolution catalyst of the formula: Sr.sub.2GaCoO.sub.5 wherein the catalyst is operated at a potential of less than 1.53 volts vs. RHE at a current density of 50 A/cm.sup.2 and a pH of 7. The oxygen evolution catalyst of formula: Sr.sub.2GaCoO.sub.5 wherein the catalyst maintains a current within 94% after 300 minutes at a potential of 1.645 volts vs. RHE wherein the current is greater than 1 milliamp and a pH of 7.

In an aspect, a ferrite composition comprises a RuCo.sub.2Z ferrite having the formula: (Ba.sub.3-xM.sub.x)Co.sub.2(MRu).sub.yFe.sub.24-2y-zO.sub.41, wherein M is at least one of Sr, Pb, or Ca; M is at least one of Co, Zn, Mg, or Cu; x is 1 to 3; y is greater than 0 to 2; and z is 4 to 4. In another aspect, an article comprises the ferrite composition. In yet another aspect, method of making the ferrite composition comprises mixing ferrite precursor compounds comprising Fe, Ba, Co, and Ru; and sintering the ferrite precursor compounds in an oxygen atmosphere to form the RuCo.sub.2Z ferrite.

A positive electrode active material has a small difference in a crystal structure between the charged state and the discharged state. For example, the crystal structure and volume of the positive electrode active material, which has a layered rock-salt crystal structure in the discharged state and a pseudo-spinel crystal structure in the charged state at a high voltage of approximately 4.6 V, are less likely to be changed by charging and discharging as compared with those of a known positive electrode active material. In order to form the positive electrode active material having the pseudo-spinel crystal structure in the charged state, it is preferable that a halogen source such as a fluorine and a magnesium source be mixed with particles of a composite oxide containing lithium, a transition metal, and oxygen, which is synthesized in advance, and then the mixture be heated at an appropriate temperature for an appropriate time.

A positive electrode active material has a small difference in a crystal structure between the charged state and the discharged state. For example, the crystal structure and volume of the positive electrode active material, which has a layered rock-salt crystal structure in the discharged state and a pseudo-spinel crystal structure in the charged state at a high voltage of approximately 4.6 V, are less likely to be changed by charging and discharging as compared with those of a known positive electrode active material. In order to form the positive electrode active material having the pseudo-spinel crystal structure in the charged state, it is preferable that a halogen source such as a fluorine and a magnesium source be mixed with particles of a composite oxide containing lithium, a transition metal, and oxygen, which is synthesized in advance, and then the mixture be heated at an appropriate temperature for an appropriate time.

A supported catalyst for decomposing an organic substance that includes a carrier and catalyst particles supported on the carrier. The catalyst particles contain a perovskite-type composite oxide represented by A.sub.xB.sub.yM.sub.zO.sub.w, where A contains at least one of Ba and Sr, B contains Zr, M is at least one of Mn, Co, Ni, and Fe, y+z=1, x>1, z<0.4, and w is a positive value that satisfies electrical neutrality. An organic substance decomposition rate after the supported catalyst is subjected to a heat treatment at 950 C. for 48 hours is greater than 0.97 when the organic substance decomposition rate before the heat treatment is regarded as 1, and an amount of the catalyst particles peeled off when the supported catalyst is ultrasonicated in water at 28 kHz and 220 W for 15 minutes is less than 1 wt % of the catalyst particles before untrasonication.

Provided is a cobalt precursor for preparing a lithium cobalt oxide of a layered structure which is included in a positive electrode active material, wherein the cobalt precursor is cobalt oxyhydroxide (CoMOOH) doped with, as dopants, magnesium (Mg) and M different from the magnesium.

A catalyst for decomposing an organic substance, the catalyst having a body which has a plurality of pores and the body contains a perovskite-type composite oxide represented by A.sub.xB.sub.yM.sub.zO.sub.w, where the A contains at least one selected from Ba and Sr, the B contains Zr, the M is at least one selected from Mn, Co, Ni, and Fe, 1.001x1.1, 0.05z0.2, y+z=1, and w is a positive value that satisfies electrical neutrality. The average pore diameter of the plurality of pores is 49 nm to 260 nm and the pore volume of each of the plurality of pores is 0.08 cm.sup.3/g to 0.37 cm.sup.3/g.

A honeycomb-structured catalyst for decomposing an organic substance, which includes a catalyst particle. The catalyst particle contains a perovskite-type composite oxide represented by A.sub.xB.sub.yM.sub.zO.sub.w, where the A contains at least of Ba and Sr, the B contains Zr, the M is at least one of Mn, Co, Ni, and Fe, y+z=1, 1.001x1.05, 0.05z0.2, and w is a positive value that satisfies electrical neutrality. The toluene decomposition rate is greater than 90% when toluene is decomposed using the honeycomb-structured catalyst subjected to a heat treatment at 1200 C. for 48 hours and a gas that contains 50 ppm toluene, 80% nitrogen, and 20% oxygen as a volume concentration as a target at a space velocity of 30,000/h and a catalyst temperature of 400 C.