Study on boron and nitrogen co-doped graphene xerogel for high-performance electrosorption application

Abstract

The search for highly efficient carbon materials with high desalting capacity for the brackish water desalination is still indispensable. In this study, boron and nitrogen co-doped graphene xerogels are prepared by a simple sol-gel method with atmospheric drying and carbonization, in which the rod-like primary particles are attached on the graphene sheets via crosslinking reaction of boric acid-melamine-resorcinol-formaldehyde (BMRF). With the increase in doping ratio, the carbonized BMRF gels display high micropore surface area and abundant doping sites. The maximum doping contents of boron (1.54 at.%) and nitrogen (8.72 at.%) can be achieved in the co-doped graphene xerogel with the molar ratios of C6H6O2 and H3BO3 of 1.2, which displays superior specific capacitance (242 F g−1 at a current density of 0.1 A g−1) and high capacitance retention (92.7% after 5000 cycles at a current density of 2.0 A g−1). The co-doped graphene xerogels are evaluated as electrode materials for the electrochemical desalination of brackish water. Compared to the bare graphene xerogel, the co-doped graphene xerogel displays high electrosorption capacity of 18.45 mg g−1 and high charge efficiency of 45% for NaCl solution under an applied voltage of 1.6 V.