A method of forming nanoporous carbon material includes the steps of providing a natural carbonaceous material, the carbonaceous material having pores being filled with at least one other material, and treating the carbonaceous material with a strong acid or a strong base, wherein the other material is removed from the pores to form a nanoporous carbon material having open pores available for organic electrolyte. The nanoporous carbon material can be used to form composite electrodes by impregnating the open pores with an organic electrolyte. Such electrodes can be used to form electrochemical double layer capacitors (EDLC), such as by disposing an electrically insulating layer comprising a plurality of nano-size dielectric particles together with a binder directly onto a surface of at least one of anode and the cathode, and interposing the electrically insulating layer between the anode and the cathode. EDLCs formed using the invention are low cost and provide large specific energy stored and low inner resistance resulting in high power output.