NOVELTY - A catalyst, comprises: a carrier; and an active metal supported on the carrier, where the carrier is crystalline carbon bonded with a functional group (I) at the surface of it.    USE - As catalyst used in a fuel cell (claimed) such as a polymer electrolyte membrane fuel cell (PEMFC) and a direct oxidation fuel cell (DOFC).    ADVANTAGE - The catalyst has improved stability and excellent catalyst performance.    DETAILED DESCRIPTION - A catalyst, comprises: a carrier; and an active metal supported on the carrier, where the carrier is crystalline carbon bonded with a functional group of formula (I) at the surface of it.    A=single bond or heterocycle;    n=0-3;    R=H, F, NH2, SH, CN, COOH, SO3H, CF3, or NO2.    Where the heterocycle is an N-containing 5- or 6-membered ring. Provided that: when A is a single bond, then n is 0-3; and when A is heterocycle, then n is 0. INDEPENDENT CLAIMS are included for the following:    (1) preparing a catalyst for a fuel cell, involving: mixing a catalyst material containing crystalline carbon and an active metal or crystalline carbon, with an aromatic amine compound in a solvent to obtain a mixture; adding sodium nitrate (NaNO2) and HCl to the mixture; agitating the mixture; and drying the agitated product;    (2) an electrode for a fuel cell, comprising: an electrode substrate; and a catalyst layer disposed on the electrode substrate, where the catalyst layer comprises the catalyst;    (3) a membrane-electrode assembly for a fuel cell, comprising a cathode and an anode facing each other; and a polymer electrolyte layer between the cathode and anode, where at least one of the cathode and anode is the electrode; and    (4) a fuel cell system, comprising: at least one electricity generating element including the membrane-electrode assembly and a separator positioned at each side of the membrane-electrode assembly, and generating electricity through oxidation of a fuel and reduction of an oxidant; a fuel supplier supplying the electricity generating element with a fuel, and an oxidant supplier supplying the electricity generating element with the oxidant.