TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preparation: No preparation method is given. Preferred Components: The electrode comprises silver colloids, silver particles, or silver nanoparticles. The electrode is a silver paste electrode. The electrode is a screen printed electrode. The surfactant is present at 0.01-0.1M. (I) in the fuel cell cathode is provided in a gas diffusion layer. The salt is present at at least 0.001M. The surfactant is dodecyl benzene sulfonic acid, sodium dodecyl sulfate (both preferred), cetyl trimethylammonium bromide, and Triton X-100 (RTM: Polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether). The salt solution is a solution comprising potassium chloride, sodium chloride, and sodium bromide. The molar ratio of surfactant to salt is 1:3. The surfactant-salt solution contains 0.033M of dodecyl benzene sulfonic acid and 0.1M of potassium chloride. The surfactant-salt solution contains 0.033M of sodium dodecyl sulfate and 0.1M of sodium chloride, contains 0.0033M of cetyl trimethylammonium bromide and 0.1M of sodium bromide, and 0.033M of Triton X-100 (RTM: Polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether) and 0.0001M of potassium chloride. (I) is a non-enzymatic catalyst, a peroxide catalyst, or hydrogen peroxide catalyst. The silver is in the form of an ink for application to the substrate. The peroxide is hydrogen peroxide. Preferred Method: The electrode is modified with the surfactant-salt solution for 3 hours. The electrode of the catalyst is coated with a coating such as Nafion (RTM: Sulfonated tetrafluoroethylene based fluoropolymer-copolymer) and/or chitosan and/or cellulose acetate. In the fuel cell cathode, silver is provided in the gas diffusion layer which is modified with a surfactant salt solution. The method-1 comprises providing a porous substrate, and applying the silver to the porous substrate. The silver is applied to the porous substrate by printing. The method-2 comprises rinsing the electrode with water before exposing the electrode to the sample. EXAMPLE - No suitable example given.