Interconnected Graphene Hollow Shells for High-Performance Capacitive Deionization

Electrochemical capacitive deionization (CDI) is a promising technology for distributed and energy-efficient water desalination. The development of high-performance capacitive electrodes is critical for enhancing CDI properties and scaling up its applications. Herein, a three-dimensional graphene porous architecture with high CDI performance is successfully constructed by assembling intentionally designed incomplete graphene-based spherical hollow shells. Small graphene oxide (GO) sheets are purposely adopted to prepare sphere shells by wrapping the surface of polystyrene sphere templates. Because the small-sized GO sheets cannot enwrap the spherical templates seamlessly, a unique graphene hollow shell structure with integrally interconnected feature forms upon removal of the templates. Compared to control samples with typical isolated pore structure (3DGA-C) prepared with commonly used large-sized GO sheets, such open and interconnected porous architectures (3DGA-OP) greatly increase their accessibility of specific surface area and pore volume, enabling superior electrochemical performance. The optimized CDI capacities of 3DGA-OP electrodes reach up to 14.4 mg·g–1 in NaCl aqueous of 500 mg·L–1 at 1.2 V, which is about 2 times the 3DGA-C ones (6.7 mg·g–1) and exceeds the CDI values of most reported pure graphene electrodes under the same experimental conditions. This strategy of improving the open interconnectivity between pores illuminates new avenues for developing high performance CDI porous electrodes assembled from two-dimensional materials.