A method of preparing a catalyst for a fuel cell includes no carbon support. The method of preparing a catalyst for a fuel cell includes preparing a first metal nanoparticle having a polyhedral shape, growing a second metal along the edge of the first metal nanoparticle, and removing the first metal nanoparticle.

Disclosed are an electrolyte membrane for fuel cells that can prevent poisoning of catalysts and a method of producing the same. The electrolyte membrane for fuel cells includes an ion transport layer including an ionomer having proton conductivity, and a catalytic composite dispersed in the ion transport layer, wherein the catalytic composite includes a catalytic particle including a catalytic metal component having an activity of decomposing hydrogen peroxide, and a protective layer formed on at least a part of a surface of the catalytic particle to prevent the ionomer from contacting the catalytic metal component.

An electrode for redox flow batteries is produced using a carbon catalyst for redox flow battery electrodes, the carbon catalyst being a particulate carbon catalyst and consisting of carbonaceous particles having a specific surface area of 800 to 2000 m.sup.2/g and an average particle size of 100 to 1000 nm.

An object of the invention is to provide an oxygen reduction catalyst composed of a titanium oxynitride having high oxygen reduction capacity. The oxygen reduction catalyst of the invention is a titanium oxynitride that has a nitrogen element content of 0.1 to 2.0 mass %, has a crystal structure of rutile titanium dioxide in a powder X-ray diffraction measurement, and has a signal intensity ratio NTiN/OTiN in an X-ray photoelectron spectroscopic analysis of in the range of 0.01 to 0.50. Further, the oxygen reduction catalyst of the invention is a titanium oxynitride that includes titanium oxide particles, has a crystal structure of rutile titanium dioxide, and has an amorphous layer in a surface layer of the titanium oxide particles.

A membrane for fuel cells, such as PEM and/or AEM fuel cells and/or electrolyzers is disclosed. Such a membrane (e.g., an anion conducting membrane) may include: crosslinked ionomer comprising two types of functional groups: a first type of functional groups forming crosslinking bonds between two ionomer chains; and a second type of functional groups comprising ion conducting functional groups. In some embodiments, the crosslinking bonds may not include the ion conducting functional groups. A catalyst coated membrane (CCM) is also disclosed. In such case the membrane may further include at least one catalyst layer attached to at least one side of the membrane to form the catalyst coated membrane (CCM). The at least one catalyst layer may include catalyst nanoparticles and crosslinked ionomer of the catalyst layer comprising two types of functional groups.

A carbon catalyst, a battery electrode, and a battery each having excellent catalytic activity and excellent durability. The carbon catalyst includes iron, exhibits a weight reduction ratio in the temperature range from 200 C. to 1,200 C. of 12.0 wt % or less measured by thermogravimetric analysis in a nitrogen atmosphere, and has a carbon structure that exhibits, in X-ray absorption fine structure analysis of a K absorption edge of the iron, the following (a) and/or (b): (a) a ratio of a normalized absorbance at 7,130 eV to a normalized absorbance at 7,110 eV is 7.0 or more; and (b) a ratio of a normalized absorbance at 7,135 eV to a normalized absorbance at 7,110 eV is 7.0 or more.

A nitrogen-containing carbon material containing a nitrogen atom, a carbon atom, and a metal element X, in which the atomic ratio (N/C) of the nitrogen atom to the carbon atom is 0.005 to 0.3, the content of the metal element X is 0.1 to 20% by mass, and the average particle diameter is 1 to 300 nm.

A method of preparing a catalyst for a fuel cell includes no carbon support. The method of preparing a catalyst for a fuel cell includes preparing a first metal nanoparticle having a polyhedral shape, growing a second metal along the edge of the first metal nanoparticle, and removing the first metal nanoparticle.

A method for synthesis of PtNi nanocages by synthesizing Pt1Ni6 nanoparticles and acid leaching to form PtNi nanocages. The acid leaching removes nickel selectively from the core of the nanoparticle.

A carbon catalyst has a carbon structure with a crystallite size Lc falling within 0.90 nm or more and 1.20 nm or less calculated through use of a Bragg angle of a diffraction peak f.sub.broad at a diffraction angle 2 of 24.04.0 obtained by separating a diffraction peak in the vicinity of a diffraction angle 2 of 26 in an X-ray diffraction pattern obtained by powder X-ray diffraction using a CuK ray, and a carbon dioxide desorption amount from 650 C. to 1,200 C. of 97 mol/g or less, a total of a carbon monoxide desorption amount and a carbon dioxide desorption amount from 650 C. to 1,200 C. of 647 mol/g or less, or a carbon monoxide desorption amount from 650 C. to 1,200 C. of 549 mol/g or less in a temperature programmed desorption method including measuring a carbon dioxide desorption amount from 25 C. to 1,200 C.