Capacitive deionization of carbon spheres with a carbon shell derived from the quantum dots of urea-citric acid grown in situ

Abstract Limited by the cost of electrode materials with a pore structure designed, there is an urgent need to prepare a low-cost carbon material with a strong salt absorption capacity (SAC) for capacitive deionization (CDI) to produce fresh water at an affordable price. The preparation of core-shell porous carbon spheres (CSs) derived from the melamine-formaldehyde (MF) spheres with a urea-citric acid quantum dot (UCQD) layer grown in situ has been reported here. Benefiting from their large specific surface area (2667.44 m2·g−1) and the uniformly doped nitrogen atoms (1.03 at.%), the prepared CSs have abundant active sites for ion absorption. Their SAC reaches up to 19.80 mg·g−1 in the NaCl solution of 1000 mg·L−1 with a working voltage of 1.2 V. Moreover, no SAC attenuation occurs after 17 cycles. This work provides a possible way to prepare low-cost core-shell CSs for CDI.