TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Assembly: The assembly (T1) further comprises a porous catalyst backing layer (preferably carbon paper or carbon cloth) with a primary surface coated with an ion-conductive and electron-conductive material which is in electronic contact with the composition (C1).    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The composition (C1) further comprises an electronically conducting polymer (H1) which forms a polymer blend with ion-conducting polymer; and a carrier carbon material for supporting the catalyst (A1) having a transition metal element. The composition (C1) comprises a catalyst (A1) dissolved or dispersed in a liquid medium; and an ion-conducting and electron-conducting polymer dissolved or dispersed in liquid medium. In the composition (C1), the catalyst (A1) or both (A1) and its supporting solid carrier is embedded in the polymer (H1).    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The coating material (G1) has an electronic conductivity of not less than 10-2 S/cm and ion conductivity of 10-3 S/cm; comprises a proton-conducting polymer (preferably poly(perfluoro sulfonic acid), sulfonated polytetrafluoroethylene, sulfonated perfluoroalkoxy derivatives of polytetrafluoroethylene, sulfonated polysulfone, sulfonated poly(ether ketone), sulfonated poly (ether ether ketone), sulfonated polystyrene, sulfonated polyimide, sulfonated styrene-butadiene copolymers, sulfonated poly chloro-trifluoroethylene, sulfonated perfluoroethylene-propylene copolymer, sulfonated ethylene-chlorotrifluoroethylene copolymer, sulfonated polyvinylidenefluoride, sulfonated copolymers of polyvinylidenefluoride with hexafluoropropene and tetrafluoroethylene, sulfonated copolymers of ethylene and tetrafluoroethylene (ETFE), polybenzimidazole (PBI), their chemical derivatives and/or copolymers; comprises an electrically conducting polymer; comprises an electrically conducting polymer selected from sulfonated polyaniline, sulfonated polypyrrole, sulfonated poly thiophene and/or sulfonated bi-cyclic polymers; comprises a mixture of an ion-conducting polymer and an electron-conducting polymer; comprises an ion-conducting polymer which is also electronically conducting. EXAMPLE - Water-soluble conductive polymers of formula (I) (in which A was H, lithium, sodium and potassium, X was sulfur, m was 4, 6, 8 or 10, and Y1 was SO3, SO4 and CO2) was prepared as described in US4880508. The surfactant molecules of the polymers (I) were sulfonate groups with sodium, hydrogen, or potassium. Conductivity of polymers (I) in a self-doped state were 10-3 to 10-2 S/cm. A doped poly(alkyl thiophene) of formula (I) (in which A was H, X was sulfur, m was 4, 6, 8 or 10, and Y1 was SO3) that exhibited an electron conductivity of 12.5 S/cm was dissolved in water. A water solution of doped poly(alkyl thiophene) of formula (I) (in which A was H, X was sulfur, m was 4, 6, 8 or 10, and Y1 was SO3) (3 wt.%) and hydrogen peroxide solution of sulfonated poly(phthalazinon ether ether ketone) (3 wt.%) was mixed and stirred at 70degrees C to obtain a polymer blend solution (J1). Carbon black-supported platinum and platinum/ruthenium catalyst particles were separately added and dispersed in the polymer blend solution (J1) to obtain an electro-catalyst composition (C2).