TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The step of grafting the porous silicon zone is controlled to form adjacent first and second areas each grouping many chemical functions of the same type. Grafting of two types of two chemical functions is obtained in a single step consisting in immersing the zone in a solution comprising ethanol, a precursor comprising a chemical function of chelating type and a precursor comprising a chemical function of reducing type, followed at least one elimination step of the precursors that did not react. The zone is grafted by the thiol chemical function and by the ethylene diamine chemical function. In the method of fabricating fuel cell, the metalized zone is formed by at least one superficial part of a side wall of a trench formed in a silicon substrate (1). Preferred Components: The metal is gold, silver, copper, platinum, ruthenium, nickel, lead, cadmium, selenium or tellurium. The porous silicon zone is mesoporous.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The chemical functions of chelating type are thiol, dithiane, ethylenediaminetetraacetic acid, thioglycolic acid, carboxylic acid, phosphonic acid, sulfonic acid and their derivatives. The chemical functions of reducing type are amine, ethylene diamine, sugar, ascorbic acid, ascorbate, hydroquinone and their derivatives. The precursors respectively comprises a chemical function of chelating type of formula (X-R-SiZ1Z2Z3) and a chemical function of reducing type of formula (X1-R1-SiZ4Z5Z6). The precursor comprises the thiol chemical function is 3-mercaptopropyltriethoxysilane and the precursor comprising the ethylene diamine chemical function is 2-(aminoethyl)aminopropyltrimethoxy or one of its oligomer. The chemical functions of reducing type are hydrazonium ions. The aqueous solution contains ethanol and hexane.R, R1 = optionally unsaturated 1-5C alkyl or phenyl;Z3, Z6 = OCH3, OC2H5, propoxy, acetoxy, Cl or H;Z1, Z2 = CH3, C2H5, propyl, isopropyl, butyl, isobutyl or Z3;Z4, Z5 = CH3, C2H5, propyl, isopropyl, butyl, isobutyl or Z6;X = chemical function of chelating type; andX1 = chemical function of reducing type. EXAMPLE - No suitable example given.