A novel electrode and method of making the same. The electrode includes activated carbon that has been modified by treatment with an alkali solution and an acid, such as nitric acid, and then washed and dried. The carbon may then be annealed. The method of modifying the activated carbon helps produce an electrode with considerably higher electric capacity and stable electric characteristics. Additionally, the electrodes may be produced more quickly and inexpensively and, therefore, permits their production of electrodes that are used for superconductors.