A gas diffusion layer having a first major surface and a second major surface which is positioned opposite to said first major surface and an interior between said first and second major surfaces is formed. The gas diffusion layer comprises a porous carbon substrate which is directly fluorinated in the interior and is substantially free of fluorination on at least one of the first major surfaces or the second major surfaces, and preferably both surfaces. The gas diffusion layer may be formed using protective sandwich process during direct fluorination or by physically or chemically removing the C—F atomic layer at the major surfaces, for example by physical plasma etching or chemical reactive ion etching.