Microporous Polycrystalline Carbon Integrated onto the Surface of Graphene Oxide Functionalized with Amino Acetaldehyde Dimethyl Acetal to Enhance Electroadsorption Desalination

Abstract

Capacitive deionization (CDI) has been considered as a promising desalination technology to solve freshwater shortages because of its superiority of low energy consumption and high efficiency. The electrode materials closely determine the desalination performance. Graded porous carbon electrode materials with rich pore structures have significant advantages. Organic molecule-functionalized graphene not only possesses three-dimensional nanostructures but also has the ability to load other micro/nanomaterials. With the assistance of ultrasound, activated carbon (AC) can be decomposed into many porous microcrystalline carbons, which can be loaded onto the surface of functional graphene through strong coupling interface interactions, forming graded porous carbon nanomaterials. The CDI device based on this structure will have excellent electroadsorption efficiency. Here, amino acetaldehyde dimethyl acetal-functionalized graphene (ADMA-GO) was synthesized via covalent modification of GO and ADMA. Subsequently, ADMA-GO was mixed with various amounts of commercially available AC by an easy ultrasound strategy. The obtained three-dimensional porous composite nanomaterial (GMAC) exhibits a suitable ion-transport pore size distribution and a large specific surface area. The GMAC-based CDI device demonstrated a superior electrosorption capacity of 17.89 mg/g at a 1.60 V applied voltage in a 50 mg/L NaCl solution, 3.52 times that of AC. This electrode also exhibited remarkable regeneration and a low energy density of 215.73 J/g. Conclusively, this study provides a strategy to enhance the electrosorption performance for low-concentration saline water (NaCl concentration <60 mg/L) in special circumstances, such as water purifiers in pacemakers and precision instruments for integrated circuit boards.