Cu-based MOF-derived architecture with Cu/Cu₂O nanospheres anchored on porous carbon nanosheets for efficient capacitive deionization

The design of high-performance electrode materials with excellent desalination ability has always been a research goal for efficient capacitive deionization (CDI). Herein, a hybrid architecture with Cu/Cu₂O nanospheres anchored on porous carbon nanosheets (Cu/Cu₂O/C) was first synthesized by pyrolyzing a two-dimensional (2D) Cu-based metal-organic framework and then evaluated as a cathode for hybrid CDI. The as-prepared Cu/Cu₂O/C exhibits a hierarchically porous structure with a high specific surface area of 305 m² g⁻¹ and large pore volume of 0.55 cm³ g⁻¹, which is favorable to accelerating ion migration and diffusion. The porous carbon nanosheet matrix with enhanced conductivity will facilitate the Faradaic reactions of Cu/Cu₂O nanospheres during the desalination process. The Cu/Cu₂O/C hybrid architecture displays a high specific capacitance of 142.5 F g⁻¹ at a scan rate of 2 mV s⁻¹ in 1 M NaCl solution. The hybrid CDI constructed using the Cu/Cu₂O/C cathode and a commercial activated carbon anode exhibits a high desalination capacity of 16.4 mg g⁻¹ at an operation voltage of 1.2 V in 500 mg L⁻¹ NaCl solution. Additionally, the hybrid CDI exhibits a good cycling stability with 18.3% decay in the desalination capacity after 20 electrosorption–desorption cycles. Thus, the Cu/Cu₂O/C composite is expected to be a promising cathode material for hybrid CDI.