TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Catalyst: The oxide catalyst is chosen from magnesium dioxide (MnO2), ruthenium oxide (RuO2), zirconium oxide (ZnO), tungsten oxide (WO3), magnesia-alumina compound (MnO2-Al2O3), ruthenium oxide-alumina compound (RuO2-Al2O3), zinc oxide-alumina compound (ZnO-Al2O3) and tungsten oxide-alumina compound (WO3-Al2O3). The transition-metal alloy catalyst is copper-nickel alloy catalyst.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Catalyst: The oxide catalyst is chosen from magnesium dioxide (MnO2), ruthenium oxide (RuO2), zirconium oxide (ZnO), tungsten oxide (WO3), magnesia-alumina compound (MnO2-Al2O3), ruthenium oxide-alumina compound (RuO2-Al2O3), zinc oxide-alumina compound (ZnO-Al2O3) and tungsten oxide-alumina compound (WO3-Al2O3). The transition-metal alloy catalyst is copper-nickel alloy catalyst.    TECHNOLOGY FOCUS - POLYMERS - Preferred Compound: The polyarylene having sulfonic acid group contains repeating units of formulae (A,B).A=bivalent electron-attractive group;B=bivalent electron-donor group or bivalent single bond;Ar=aromatic group having substituent of formula (-SO3H);m,n=0-10;k=1-4;R1-R8=hydrogen, fluorine, alkyl, fluorine-substituted alkyl, allyl, aryl or cyano;W=bivalent electron-attractive group or bivalent single bond;T=single bond or divalent organic group;andp=0 or positive integer. SPECIFIC COMPOUNDS - The macrocyclic metal-complex catalyst is chosen from iron phthalocyanine (C32H16N8Fe), copper-phthalocyanine (C32H16N8Cu), zinc phthalocyanine (C32H16N8Zn), and cobalt phthalocyanine (C32H16N8Co).    EXAMPLE - Polyarylene having number average molecular weight of 53200, weight average molecular weight of 185000 and sulfonic-acid equivalence of 1.9 meq/g, was prepared by reacting 4-(4-(2,5-dichloro benzoyl)phenoxy)benzene sulfonic acid neopentyl) and oligomer of formula (I). The obtained polyarylene (in g) (50), magnesium dioxide (5) having specific surface of 60 m2/g and N-methyl-2-pyrrolidone (312) were added to a poly bottle, and stirred by a disperser for 20 minutes. The obtained solution was cast on a polyethylene terephthalate film, and dried at 80degreesC for 30 minutes and 150degreesC for 60 minutes, to form manganese dioxide-containing solid electrolyte film of 50 microns thickness. The obtained film was subjected to hydrogen-peroxide decomposition test, by immersing the film in hydrogen peroxide solution for 10 hours. The result showed that the film had small change in weight and the shape of the film was retained. A fuel cell was produced using the obtained film. The voltage of fuel cell between each terminal in current density of 0.5 A/cm2 and 1 A/cm2 were found to be 0.75 V and 0.6 V, respectively. The reduction in voltage between terminals after continuous discharge-test of fuel cell for 3000 hours in current density of 0.5 A/cm2 was 5% or less. The results showed that the electrolyte film was stable in hydrogen-peroxide solution, and was excellent in durability.