Synergistic effect of intercalation and EDLC electrosorption of 2D/3D interconnected architectures to boost capacitive deionization for water desalination via MoSe2/mesoporous carbon hollow spheres

Abstract

Transition-metal dichalcogenides can be used for capacitive deionization (CDI) via pseudocapacitive ion intercalation/de-intercalation due to their unique two-dimensional (2D) laminar structure. MoS₂ has been extensively studied in the hybrid capacitive deionization (HCDI), but the desalination performance of MoS₂-based electrodes remains only 20-35 mg g^-1 on average. Benefiting from the higher conductivity and larger layer spacing of MoSe₂ than MoS₂, it is expected that MoSe₂ would exhibit a superior HCDI desalination performance. Herein, for the first time, we explored the use of MoSe₂ in HCDI and synthesized a novel MoSe₂/MCHS composite material by utilizing mesoporous carbon hollow spheres (MCHS) as the growth substrate to inhibit the aggregation and improve the conductivity of MoSe₂. The as-obtained MoSe₂/MCHS presented unique 2D/3D interconnected architectures, allowing for synergistic effects of intercalation pseudocapacitance and electrical double layer capacitance (EDLC). An excellent salt adsorption capacity of 45.25 mg g^- ¹ and a high salt removal rate of 7.75 mg g^- ¹ min^-1 were achieved in 500 mg L^- ¹ NaCl feed solution at an applied voltage of 1.2 V in batch-mode tests. Moreover, the MoSe₂/MCHS electrode exhibited outstanding cycling performance and low energy consumption, making it suitable for practical applications. This work demonstrates the promising application of selenides in CDI and provides new insights for ration design of high-performance composite electrode materials.