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

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.