A process for the preparation of carbon layers on powdered supports comprising dissolving a hydrophilic polymer (PH) at the level of 85 do 99.9% by weight in water, adding pyromellitic acid (PMA) or pyromellitic dianhydride (PMDA) at the level of 0.1-15% by weight, then introducing to the mixture the powdered support at a level of 1-99% by weight. The suspension is concentrated and dried, and the composite precursor formed is subjected to a pyrolysis process at 300-1500° C.