Abstract: The nitrogen and phosphorus co-doped crystalline carbon materials are prepared by a template-free method that includes pyrolizing a precursor mixture including a carbon source, a nitrogen source, and a phosphorus source. The method involves mixing known amounts of the precursor components, dissolving the precursor mixture in deionized water, distilling solvent from the aqueous mixture, and vacuum drying the residue to a dry solid mixture. The mixture is then carbonized by pyrolysis at 900° C. in an argon atmosphere to obtain a nitrogen and phosphorus co-doped crystalline carbon material. The principles of the method are illustrated by a precursor mixture of sucrose, urea, and ammonium dihydrogen phosphate (NH4H2PO4). The amount of ammonium salt in the precursor mixture plays a key role in controlling the crystallinity, morphology, and composition of the N/P co-doped crystalline carbon material.