TECHNOLOGY FOCUS - TEXTILES AND PAPER - Preferred Non-woven Web: The non-woven web comprises 80 wt.% of long fibers and 20 wt.% or more of short fibers. The non-woven web comprises no more than 85 wt.%, preferably 70 wt.% of short fibers to the total amount of fibers. The long fibers having average length of 5-30 mm, has maximum average length of 50 mm. The short fibers having average length of less than 2 mm, preferably less than 1 mm has average minimum length of 50 microns. The long and short fiber is carbon, glass, silica, polymer, metal or ceramic fibers. Preferably, the long and short fiber is carbon fiber and the non-woven web has density of 0.1-0.2 g/cm3.Preferred Filler Material: The filler material in the gas diffusion substrate comprises particulate carbon, polymer and catalyst material.Preferred Electrocatalyst Material: The electrocatalyst material in the gas diffusion electrode comprises electrocatalytic component(s) and polymer. The electrocatalyst material is a precious metal or transition metal as metal or its oxide, which is either (un)supported in a dispersed form on carbon support and/or carbon or organic complex in the form of high surface area finely divided powder or fiber.Preferred Process: To membrane electrode assembly which comprises second gas diffusion substrate (which may or may not be a substrate), electrocatalyst layer is applied to a side of solid polymer membrane facing the gas diffusion substrate (which may or may not be a substrate). EXAMPLE - Chopped carbon fibers (1.0 g) each at a fiber lengths of 6 mm and 12 mm, carbon fiber wool (1.0 g) and polyvinyl alcohol fibers (2.0 g) were dispersed in water and from the dispersion a non-woven sheet was created. The sheet was dried and had density of 0.116 g/cm3. Non-woven carbon fiber sheet was placed on polytetrafluoroethylene sheet (PTFE) and sprayed with a suspension of PTFE (2.3 g) in water (10 g). Half of the suspension was sprayed on first side of sheet and dried. Then, remaining suspension was sprayed on other side of sheet, dried. Resulting sheet was fired to give 30% loading of PTFE.    Particulate material as filler material (for embedding within fiber network was prepared by dispersing 47 weight parts of acetylene black in 1200 wt.pts of water followed by adding and mixing 3 wt.pts of PTFE) was pressed into sheet, dried. Then, thin layer of particulate material was applied to same side. The structure was sandwiched between 2 filter papers and passed through rollers to compact the layer. The sheet was dried and process was repeated for second side. Thin layers of the particulate material were applied alternately to each side with compaction and drying, until a loading of 3.33 mg/cm2 of carbon was achieved.    Resulting gas diffusion substrate sheet was fired. Catalyst material was used for forming electrocatalyst layer on gas diffusion substrate. Electrocatalyst layer was then applied to top face of filled substrate to give a platinum load. Electrode formed cathode of membrane electrode assembly (MEA) with platinum catalyst layer bonded to membrane electrolyte face. Membrane employed was Nafion 112 (RTM).