The structural evolution of 3D-RGO with reduction temperature and its effect on capacitive deionization performance

Abstract

The structure control of electrode materials was one of the sticking points in capacitive deionization (CDI). In this work, a 3D cross-linked reduced graphene oxide (3D-RGO) was synthesized to effectively solve the problem of agglomeration during the reduction process. The effect of 3D-GO reduction temperature on its structure, surface functional groups, and CDI performance has been systematically analyzed. When the temperature is below 650 °C, a certain amount of functional groups remain on the 3D-RGO, which leads to an anti-CDI phenomenon due to the co-ion expulsion effect. Too high reduction temperature (above 1050 °C) will cause the collapse of the 3D-RGO framework, which results in the specific surface area and CDI performance decrease. The preferred reduction temperature is 850 °C, which results in a high specific surface area (447 m² g⁻¹), fewer surface functional groups, and abundant macropores and mesopores. This also achieves the highest desalination capacity of 8.7 mg g⁻¹ at a voltage of 1.6 V in 100 mg L⁻¹ NaCl solution. The open and interconnected porous structure of the 3D-RGO framework provides an effective substrate for later loading and modification.