N, P, S co-doped hollow carbon polyhedra derived from MOF-based core–shell nanocomposites were developed for capacitive deionization.

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.

Removal of ions from saline water has been demonstrated by using N, P co-doped 3D hierarchical carbon via capacitive deionization.

Capacitive deionization (CDI) is an alternative water purification technology.