N,P-Codoped Meso-/Microporous Carbon Derived from Biomass Materials via a Dual-Activation Strategy as High-Performance Electrodes for Deionization Capacitors

Nitrogen and phosphorus codoped meso-/microporous carbon derived from biomass materials has been designed and successfully fabricated as high-performance electrodes for deionization capacitors. The obtained materials were prepared by the pyrolysis of pomelo peel via a dual-activation strategy by using NH 4 H 2 PO 4 and KHCO 3 . It is interesting that the as prepared nitrogen and phosphorus codoped meso-/microporous carbon possesses a high specific surface area of 2726 m 2 g –1 with high percentage of mesopores of 52%. It has been demonstrated that the obtained electrode shows high specific capacitance, low inner resistance and good wettability. Consequently, the obtained electrode exhibits good deionization performance in a 300–1000 mg L –1 NaCl solution at 1.0–1.4 V with a flow rate of 20–60 mL min –1 . The electrode reveals an ultrahigh deionization capacity of 20.78 mg g –1 at 1.4 V in a 1000 mg L –1 NaCl solution. The regeneration performance of the obtained electrode is good. The good performance is ascribed to the high specific surface area, superior micro-/mesoporous structure, and N,P-codoping. Hence, the nitrogen and phosphorus codoped meso-/microporous carbon should be a promising candidate as electrode material for deionization capacitors. The present work paves a way for the development of multiheteroatom codoped meso-/microporous carbon materials for electrochemical applications.