NOVELTY - Providing fuel cells that are less expensive to manufacture and/or more efficient to operate and which have reduced crossover, are thinner and/or has improved catalyst accessibility.    USE - For generating electricity.    ADVANTAGE - The fuel cell is manufactured economically and is efficiently operated. The fuel cell has reduced cross over. The thin active layer in the gas diffusion electrode has improved catalyst accessibility. The modified carbon product eliminates the usage of fluoropolymer binder and also improves catalyst activity and mass transport. The elimination of fluorine polymer binder greatly reduces cost of the electrodes, and thus very economical electrodes are obtained. The organic group in the carbon product allows the catalyst particle in the catalyst layer to be in close proximity to the organic group and excellent catalyst utilization is obtained. By using modified carbon product in the catalyst layer, the thickness of the catalyst layer is reduced, since the need for the binder is reduced, or completely eliminated. By using the modified carbon product, the thickness of the solid electrolyte membrane is reduced without affecting crossover, and reduced crossover permits use of thinner membrane which results in diminished ohmic losses in the fuel cell. The modified carbon product provides hydrophobic and/or hydrophilic properties and is not randomly wetted. The wetting characteristics of the carbon product is uniformly distributed in the active layer. Thus, the unwanted excessive wetting of the carbon product is avoided, and thus service life of the electrode is improved. The blocking layer effectively blocks the electrolyte and permits greater air diffusion.    DETAILED DESCRIPTION - A fuel cell has a gas diffusion electrode, and a gas diffusion counter-electrode, and a solid electrolyte membrane provided between the electrode and counter-electrode. The electrodes comprise modified carbon product(s) such as a carbon product having at least one organic group attached.    INDEPENDENT CLAIMS are included for the following:    (1) a method of reducing the thickness of the solid electrolyte membrane, which involves forming electrolyte membrane with the modified carbon product;    (2) a method of increasing catalyst accessibility in an electrode, which involves forming an active layer with the modified carbon product in the absence of a fluoropolymer binder;    (3) a modified carbon product which is a carbon product having attached at least one ionic group associated with a counter ionic catalyst group;    (4) formation of carbon substrate containing catalyst, which involves reacting a modified carbon product having attached at least one ionic group, with a counter ionic catalyst precursor to form a modified carbon product having attached at least one ionic group associated with a counter ionic catalyst group, and reducing counter ionic catalyst with at least one reducing agent to form a catalyst. The catalyst is uniformly distributed throughout the modified carbon product; and    (5) a membrane which has a layer (I) comprising a modified carbon product and optionally at least one binder, and a layer (II) comprising at least one hydrophobic polymer.