TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Component The redox catalyst is an enzyme, e.g. oxido-reductase.    TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Component: The cathode is configured and arranged for electro-reducing oxygen. The cathode and anode comprise porous current collector having an electrical conducting material in contact with a multitude of domains each containing a redox catalyst and an electron transport mediator. The redox catalyst and electron transport mediator are in fluid association with each other within the domain. They are bounded in the domain by the porous current collector and a containment material. The containment material is a film. The porous current collector comprises an electrical conducting material.Preferred Dimension: The domain has a diameter of less than 100 microns.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The reductant can be hydrogen, alcohols, carbohydrates, carboxylic acids or carboxylic esters. The alcohol is methanol. The carbohydrate is glucose. The carboxylic acid is formic acid. The carboxylic ester is methyl formate. The electron transport mediator is quinones, hydroquinones, metalloorganic complexes, conjugated unsaturated acyclic and cyclic molecules, metal ions or biological electron carriers. It can be 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate).    TECHNOLOGY FOCUS - POLYMERS - Preferred Material: The containment material is polyelectrolyte polymers, permeable polymers, porous metal oxide-based coatings, organically modified metal oxides, fluorine-containing polymers, silica or colloidal carbon emulsions. The film is made of silica, titania, alumina, polyesters, polyamides, polyimides, fluoropolymers, polyelectrolytes, organosubstituted silica, silicones, organosubstituted titania or organo metal oxides. The electrical conducting material is carbon paper, carbon paste, carbon nanotubes, carbon particles, conducting polymers, noble metal particles or conducting metal oxide particles.