A method for producing a fuel cell electrode catalyst, including a step (I) of bringing an aqueous solution of a transition metal compound (1) into contact with ammonia and/or ammonia water to generate a precipitate (A) containing an atom of the transition metal, a step (II) of mixing at least the precipitate (A), an organic compound (B), and a liquid medium (C) to obtain a catalyst precursor liquid, and a step (IV) of subjecting the solid in the catalyst precursor liquid to heat treatment at a temperature of 500 to 1200 C. to obtain an electrode catalyst; a portion or the entirety of the transition metal compound (1) being a compound containing a transition metal element of group 4 or group 5 of the periodic table; and the organic compound (B) being at least one selected from sugars and the like.

To provide a process for producing a liquid composition capable of forming a polymer electrolyte membrane of which breakage at the time of drying is suppressed; a process for producing a catalyst layer-forming coating liquid capable of forming a catalyst layer of which breakage at the time of drying is suppressed; and a method for producing a membrane/electrode assembly by which a catalyst layer or a polymer electrolyte membrane of which breakage at the time of drying is suppressed, can be formed.

A process for producing a liquid composition, which comprises holding a fluorinated polymer having SO.sub.2F groups at from 110 to 130 C. for at least 45 minutes; cooling the fluorinated polymer having SO.sub.2F groups held at from 110 to 130 C. to less than 110 C.; converting the SO.sub.2F groups in the fluorinated polymer having SO.sub.2F groups cooled to less than 110 C. to ion exchange groups thereby to obtain a fluorinated polymer having ion exchange groups; and mixing the fluorinated polymer having ion exchange groups and a liquid medium.

An object is to provide a catalyst particle that can exhibit high activity. The catalyst particle is an alloy particle formed of platinum atom and a non-platinum metal atom, wherein (i) the alloy particle has an L1.sub.2 structure as an internal structure and has an extent of ordering of L1.sub.2 structure in the range of 30 to 100%, (ii) the alloy particle has an LP ratio calculated by CO stripping method of 10% or more, and (iii) the alloy particle has a d.sub.N/d.sub.A ratio in the range of 0.4 to 1.0.

A hybrid catalyst for a fuel cell includes a noble metal-based catalyst; and a non-noble metal-based catalyst on which the noble metal-based catalyst is supported. The noble metal-based catalyst comprises at least one of platinum (Pt), palladium (Pd), iridium (Ir), and gold (Au). The noble metal-based catalyst comprises a porous carbon having a first pore and a second pore smaller than the first pore.

A cathode for fuel cells includes a carbon support, a platinum catalyst supported on the carbon support and an ionomer surrounding the carbon support and the platinum catalyst, wherein the ionomer is removed from the surface of the platinum catalyst. The cathode for fuel cells has a structure in which an ionomer film coating the surface of the platinum catalyst and thus acting as oxygen transfer resistance is removed from the surface of the platinum catalyst and, thus, mass transfer resistance (oxygen diffusion resistance) may be reduced and performance of a fuel cell may be improved. Further, the cathode having a low amount of platinum used due to improvement in platinum utilization may effectively execute oxygen transfer and thus increase the amount of platinum participating in catalysis, as compared to conventional cathodes.

A method for improving freezing resistance of a membrane electrode assembly is provided. In particular, the method improves freezing resistance of a membrane electrode assembly including conducting drying and heat treatment under certain conditions to produce an electrode that reduces formation of macro-cracks and micro-cracks in the electrode. Accordingly, water does not permeate the electrode excessively and the electrode does not break even when frozen.

The invention relates to a cathode for a metal/air battery comprising at least one active layer produced in an active material and having an air side and a metal side, a current collector and a hydrophobic membrane produced in a hydrophobic material and deposited on the air side of the active layer. Said hydrophobic material has a porous structure and has penetrated into the air side of the active layer so as to form, between the hydrophobic membrane and the active layer, an interpenetration zone of hydrophobic material in the active material, in which there is a concentration gradient of hydrophobic material which decreases in the ingoing direction of air into the cathode.

A method for manufacturing a catalyst for fuel cell includes: providing or receiving magnesium porphyrin-containing powder; mixing the magnesium porphyrin-containing powder with a carbon-containing carrier powder to form a first mixture, and performing a thermal treatment to pyrolzye the first mixture to form the catalyst for fuel cell. A catalyst for fuel cell is also provided herein.

A fuel cell electrode catalyst includes a carbon support having pores, and catalyst particles supported on the carbon support and containing platinum or a platinum alloy. The pores of the fuel cell electrode catalyst have a mode pore size within a range from 2 nm to 5 nm. In the pores of the fuel cell electrode catalyst, a pore volume of pores having pore sizes within the range from 2 nm to 5 nm is 0.4 cm.sup.3/g or larger. The catalyst particles have a crystallite size within the range from 2 nm to 5 nm at a platinum (220) plane. A density of the supported catalyst particles is within a range from 10% by mass to 50% by mass with respect to a total mass of the fuel cell electrode catalyst.

A membrane/electrode assembly of a fuel cell using a film obtained by molding a mixture in which a synthetic resin and a solvent are mixed with fullerene nanowhisker/nanofiber nanotubes supporting a catalyst or including a catalyst in fullerene crystals, wherein the fullerene nanowhisker/nanofiber nanotubes are obtained by uniformly stirring and mixing a solution containing a first solvent having fullerene dissolved therein, and a second solvent in which fullerene is less soluble than that in the first solvent, in a thin film fluid formed between processing surfaces arranged to be opposite to each other so as to be able to approach to and separate from each other, at least one of which rotates relative to the other, and the resultant fullerene nanowhisker/nanofiber nanotubes are heated at 300 C. to 1000 C. in a vacuum heating furnace.