Capacitive Deionization of Saline Water by Using MoS₂-Graphene Hybrid Electrodes with High Volumetric Adsorption Capacity

Capacitive deionization (CDI) has received wide attention as an emerging water treatment technology because of its low energy consumption, low cost, and high efficiency. However, the conventional carbon electrode materials for CDI have low densities, which occupy large volumes and are disadvantageous for use in limited space (e.g., in household or on offshore platforms). In order to miniaturize the CDI device, it is quite urgent to develop high volumetric adsorption capacity (VAC) electrode materials. To overcome this issue, we rationally designed and originally developed high VAC MoS₂-graphene hybrid electrodes for CDI. It is interesting that MoS₂-graphene hybrid electrode has a much higher NaCl VAC of 14.3 mg/cm³ with a gravimetric adsorption capacity of 19.4 mg/g. It has been demonstrated that the adsorption capacity is significantly enhanced because of the rapid ion transport of MoS₂ and high electrical conductivity of graphene. In situ Raman spectra and high-angle annular dark-field scanning transmission electron microscopy tests demonstrated a favorable Faradaic reaction, which was crucial to enhancing the NaCl VAC of the MoS₂-graphene hybrid electrode. This work opens a new avenue for miniaturizing future CDI devices.