Polyaniline-derived nitrogen-doped carbon/MoS2 nanocomposites as cathode for efficient hybrid capacitive deionization

Abstract

Molybdenum disulfide (MoS2) has become an attractive faradic material for capacitive deionization (CDI) process, but it still suffers from several drawbacks, such as low electrical conductivity, inferior hydrophilicity and easy restacking. Hence, we integrated MoS2 with high nitrogen content carbonized polyaniline (MoS2/CP) as intercalation cathode for CDI. The disordered entanglement between MoS2 and CP nanosheets enlarged interlayer spacing, improved pore structure and surface area which can provide multiple charge transfer routes and endow more embedding sites to storage Na+. The Mo-N-C bonds improve the electrical conductivity and wettability to facilitate ions diffusion process as well as ensure the cyclic stability of composites electrode. Moreover, the charge transfer between Na+ and N-containing functional groups is beneficial to forming pseudo-capacitance. Accordingly, the MoS2/CP electrode possess a large specific capacitance of 99.1 F g-1 at 5 mV s-1, which is 36% higher than MoS2. The hybrid cell AC//MC-2 delivers a remarkable desalination capacity (29.14 mg g-1), a rapid desalination rate (2.9 mg g-1 min-1) and favorable cyclic durability at 1.2 V in 500 mg L-1 NaCl solution. The superior desalination performance of MoS2/CP electrode was evaluated based on a capacitance-controlled contribution of 85.8% and a diffusion-controlled contribution of 14.2%.