Constructing a high-performance nitrogen-doped three-dimensional framework graphene material for efficient capacitive deionization

Abstract

The reduced graphene oxide material has great potential application in capacitive deionization (CDI), however, its slow adsorption rate and poor cycle stability have restricted its industrial application. In this work, a kind of nitrogen-doped framework reduced graphene oxide aerogel (NFGA) was designed and prepared for CDI. Therein, acrylamide was utilized as a nitrogen source, and ammonium persulphate was used as the initiator for the polymerization reaction of the three-dimensional structure. The results showed that the material exhibited a high specific capacitance value of 235.3 F·g−1 with the desalination capacity of the NFGA electrode of 25.76 mg·g−1. The adsorption time of 10-min was sufficient to reach the reaction equilibrium in practical CDI device usage. As energy consumption for removal of NaCl (1.2 V 500 mg·L−1), the electrode consumed 5.56 × 10−2 Wh·g−1 and 1.11 × 102 Wh·m−3 with consideration of peristaltic pump energy. Furthermore, the density functional theory calculations demonstrated that the total density of states of pyridinic N and pyrrolic N were consistently higher than that of graphene near the highest occupied molecular orbital (HOMO) level, which were significantly lower (−1.35 and −1.46 eV) than the adsorption energy on the graphene surface (−0.95 eV).