TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred System: The fuel cell system comprises a membrane electrode assembly having an air electrode in one surface of a solid polymer electrolyte membrane, and a fuel electrode in the other surface. An air-electrode side separator arranged at the air-electrode side of the membrane electrode assembly forms an airflow path between the assemblies, and a fuel-electrode side separator arranged at the fuel-electrode side of the membrane electrode assembly forms a fuel-gas flow path between the assemblies. A supplier is provided for supplying the organic mediator from the air-electrode side or fuel-electrode side. The organic mediator is continuously supplied to the fuel electrode as mediator aqueous solution enclosed in a tank. The solution is supplied to the fuel electrode by a liquid-feeding pump. The tank and pump, and the solution supply line and pipe are connected by a pipe line. The organic mediator is supplied to the fuel electrode, sent to the air electrode by concentration gradient, oxidized by catalyst, and discharged as carbon dioxide, water-vapor, or nitrogen. The electroconductive base material is a catalyst layer comprised in the fuel electrode or air electrode.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Mediator: The organic mediator is fixed by the functional group by hydrogen bond. The organic mediator is fixed by the particles in the chemical bond with the functional group. The organic mediator is a hydrocarbon-type compound comprising 4 atoms of carbon, oxygen, nitrogen and hydrogen, and has a standard oxidation reduction potential larger than 0.68 V (normal hydrogen electrode) and smaller than 2.85 V, preferably smaller than 1 V (normal hydrogen electrode). The organic mediator is a nitrogen-containing compound of formula: R1-N(-R2)=X, preferably compound of formula (12), or an imide compound of formula (1), preferably of formulae (2-8).R1,R2=substituents;X=oxygen or hydroxyl;Y1=aromatic or non-aromatic 5-12-membered ring having double bond;R3,R4=H, halogen, alkyl, aryl, cycloalkyl, hydroxyl, alkoxyl, carboxyl, alkoxycarbonyl, or acyl;R5-R8=H, halogen, alkyl, hydroxyl, alkoxyl, carboxyl, alkoxycarbonyl, acyl, nitro, cyano, or amino;n=1-3;andR21-R23=optionally substituted alkyl.R1 and R2 mutually couple to form double bond, aromatic ring, or non-aromatic ring. R3 and R4 combine with each other to form double bond, aromatic ring, or non-aromatic ring, preferably 5-12-membered aromatic or non-aromatic ring chosen from cycloalkane, cycloalkene, cross-linking type hydrocarbon ring, aromatic ring, and/or their substitution products. R21-R23 may combine with each other to form ring including oxygen and nitrogen. The imide compound is N-hydroxy succinic acid imide, N-hydroxy maleic acid imide, N-hydroxy hexahydrophthalic imide, N,N'-dihydroxy cyclohexane tetracarboxylic acid imide, N-hydroxy phthalimide, N-hydroxy tetrabromo phthalic imide, N-hydroxy tetrachloro phthalic acid imide, N-hydroxy HET-acid imide (sic), N-hydroxy himic acid imide, N-hydroxy trimellitic acid imide, N,N'-dihydroxy pyromellitic acid imide, and/or N,N'-dihydroxy naphthalene tetracarboxylic acid imide. The imide compound (1) is of formula (9), preferably of formula (10 or 11).R9-R14=H, alkyl, aryl, cycloalkyl, hydroxyl, alkoxy, carboxyl, substituted oxycarbonyl, acyl, or acyloxy;andR15-R20=H, alkyl, hydroxyl, alkoxyl, carboxyl, alkoxycarbonyl, acyl, nitro, cyano, or amino.At least two of R9-R14 combine with each other to form double bond, aromatic ring, or non-aromatic ring with at least one ring having N-substituted cyclic imide group. Compound (9, 10 or 11) is N-hydroxy glutaric acid imide, N-hydroxy-1,8-naphthalene dicarboxylic acid imide, N-hydroxy-1,8-decalin dicarboxylic acid imide, N,N'-dihydroxy,1,8;4,5-naphthalene tetracarboxylic acid imide, N,N'-dihydroxy-1,8;4,5-decalin tetracarboxylic acid imide, and/or N,N',N"-trihydroxy isocyanuric acid. Compound (12) is of formula (13), preferably of formula (14), more preferably of formula (15, 16 or 17).R21-R23=as mentioned above;R24-R26=R21;andZ=optionally substituted alkyl (oxygen and nitrogen may be included), optionally substituted aryl (oxygen and nitrogen may be included), alkoxy, carboxyl, alkoxycarbonyl, cyano, hydroxyl, nitro, amino, or H.R21 and R22 couple together and ring Y2 forms 5- or 6-membered ring. Preferred Groups: The functional group is carboxyl, hydroxyl, alkoxyl, alkoxycarbonyl, acyl or sulfone group, preferably carboxyl group. The chemical bond is hydroxyl group or amino group introduced into the organic mediator, and is a bond by reaction with carboxyl group.    TECHNOLOGY FOCUS - POLYMERS - Preferred Properties: The organic polymeric fine particles have an average particle diameter of 0.1-1000 microns, preferably 10-100 microns. Preferred Resin: The polymer used as base for organic polymeric fine particles is phenol resin, urea resin, melamine resin, unsaturated polyester, epoxy resin, polyimide resin, polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylic resin, polyacetal, polyamide, polycarbonate, polybutylene terephthalate resin, polyethylene terephthalate resin, polyphenylene sulfide resin, polysulfone, polyether ether, polyether sulfone, polyether imide, and/or polyether ketone, preferably polyethylene, polypropylene, polystyrene, acrylic resin, or polymer into which carboxyl group is introduced by oxidation treatment. The organic polymeric fine particles contain the reaction intermediate of condensation polymer obtained by condensing carboxylic acid as monomer in which carboxyl group produced by reacting monomer having excess carboxylic acid substituents than dicarboxylic acid remains. The reaction intermediate contains polyimide resin, polyamide, polycarbonate, polybutylene terephthalate resin, polyethylene terephthalate resin, polyphenylene sulfide resin, and/or polyether imide.