Dual-confinement effect in metal oxide nanoparticles/MXene-reduced graphene oxide for high capacitive deionization performance

Metal oxide nanoparticles are one kind of important electrode materials for capacitive deionization (CDI) application. Unfortunately, most metal oxide materials usually exhibit poor electrical conductivity and often experience slow dissolution of metallic species, thereby resulting in limited desalination performance. Overcoming these obstacles still remains challenging due to the lack of synthetic approaches. Taking it into consideration, herein we proposed a dual confinement strategy to promote the CDI application of metal oxide nanoparticles. Nb₂O₅ was synthesized as a typical example for designing metal oxide/MXene-reduced graphene oxide (rGO) derived from Nb₂CT_x MXene/graphene oxide (GO) under hydrothermal condition. In the hybrid, Nb₂CT_x and rGO serve as both the confinement agent and conductive support for Nb₂O₅ nanoparticles, endowing Nb₂O₅/Nb₂CT_x-rGO with improved electronic conductivity and structural stability. As a result, the hybrid shows an outstanding desalination performance, including a NaCl adsorption capacity of 41.07 mg g⁻¹, an ultra-fast average NaCl adsorption rate of 4.14 mg g⁻¹ min⁻¹ and excellent long-term cycling stability of 50 cycles (81 % desalination capacity retention rate). This work is expected to bring new insights in the synthesis of metal oxide materials for electrochemical desalination.