Abstract: The present invention is, in one aspect, a process for removing low-valent sulfur from carbon containing such low-valent sulfur (sulfur-containing carbon), having the step of contacting the sulfur-containing carbon with a platinum oxide in an aqueous environment, for a time sufficient to remove a desired amount of low-valent sulfur from the sulfur-containing carbon, especially from the surface of the carbon. Another aspect of the invention is an electrode, comprising an electrocatalyst or active material for a fuel cell or battery, disposed in a carbon matrix, where the carbon matrix is essentially free of low-valent sulfur adjacent to the active material of the battery electrode or electrocatalyst of the fuel cell electrode. Such an electrode will be suitable for use in a fuel cell or in a battery. Another aspect of the invention is a fuel cell or a battery using this electrode.