Patent ID: 7022426

Claim:
A solid polymer fuel cell comprising an electrolyte membrane having an aromatic hydrocarbon polymer ion-exchange component, and an air electrode and a fuel electrode between which said electrolyte membrane is sandwiched, each of said air electrode and said fuel electrode being formed of a plurality of catalyst particles including a catalyst metal carried on surfaces of carbon black particles, and an aromatic hydrocarbon polymer ion-exchange component which is the same as or different from the aromatic hydrocarbon polymer ion-exchange component of said electrolyte membrane, said fuel cell being moistened from both of the side of said air electrode and the side of said fuel electrode, wherein said carbon black particles have a water-repellent property such that an amount A of water adsorbed under a saturated steam pressure at 60° C. is equal to or smaller than 80 cc/g, and if a weight of polymer ion-exchange component incorporated is represented by Wp, and a weight of carbon black particles incorporated is represented by Wc, a ratio Wp/Wc of the weight Wp of polymer ion-exchange component incorporated to the weight Wc of carbon black particles incorporated is in a range of 0.4≦Wp/Wc≦1.25; and wherein said polymer ion-exchange component in each of said air electrode and said fuel electrode is a sulfonated aromatic hydrocarbon polymer, and wherein a degree D of dispersion of said catalyst particles in each of said air electrode and said fuel electrode is in a range of 3%≦D≦8%, each of said degrees D of dispersion of said catalyst particles being determined according to D =({( Ts/Tp )−( As/Ap )}/( Ts/Tp ))×100 (%) wherein Tp represents a theoretical concentration of a catalyst metal in the catalyst particles; Ts represents a theoretical concentration of sulfur (S) in said sulfonated aromatic hydrocarbon polymer; Ap represents an actual concentration of the catalyst metal in the catalyst particles; and As represents an actual concentration of sulfur (S) in said sulfonated aromatic hydrocarbon polymer.