Pseudo-capacitive behaviors induced dual-ion selective deionization system based on MoS2/PPy//Ag@PANI/AC

Hybrid capacitive deionization (HCDI) is an innovative CDI technology that outperforms conventional CDI concerning desalination capability and charge efficiency. However, underutilized cathodes or anodes and mismatched kinetic behavior remain unsatisfactory given the imbalanced device architecture consisting of the capacitor and Faraday electrodes. Herein, we proposed a pseudo-capacitive behaviors induced dual-ion selective deionization (Di-CDI) strategy where molybdenum disulfide/polypyrrole (MoS 2 /PPy) acted as Na + intercalation cathode, and Ag-coated polyaniline-modified activated carbon (Ag@PANI/AC) served as Cl − trapping anode. In this system, the hollow PPy nanotube as the core is anchored by ultrathin MoS 2 nanoflakes, connecting loose MoS 2 nanoflowers to form a 3D flower-chain network, which holds convenient electron transfer routes and fast charge transport channels, facilitating accelerated ion diffusion process. Besides, Ag@PANI/AC was synthesized by modifying Ag particles on a 3D electron conduction substrate constructed by coupling PANI and AC, where Ag is responsible for the conversion reaction with Cl − to create AgCl. The conduction matrix compensates for the low conductivity of AgCl, enabling fast adsorption kinetics. As expected, the assembled Di-CDI system MoS 2 /PPy//Ag@PANI/AC delivers an excellent adsorption capacity of 25.1 mg g -1 , outstanding desalination rate (5.88 mg g -1 min -1 ), superior cycle stability (91.5% retention rate), and promoted charge efficiency of 56.2%, validating that this strategy supplies a viable way to achieve more energy-efficient CDI.