An electric motive power system for a motor vehicle including a fuel cell having at least one set of two electrodes each provided with an electrode input and output, an electrolytic membrane being located between the two electrodes. The electrolytic membrane includes proton conductive charges distributed in the thickness of the membrane in accordance with a concentration gradient, to concentrate the water in liquid form produced by the fuel cell on one of the electrodes, and wherein the water in liquid form thus concentrated is evacuated from the fuel cell through a single electrode output.