Two-dimensional
(2D) layered transition-metal carbides (MXenes)
are attractive faradic materials for an efficient capacitive deionization
(CDI) process owing to their high capacitance, excellent conductivity,
and remarkable ion storage capacity. However, the easy restacking
property and spontaneous oxidation in solution by the dissolved oxygen
of MXenes greatly restrict their further application in the CDI domain.
Herein, a three-dimensional (3D) heterostructure (MoS2@MXene)
is rationally designed and constructed, integrating the collective
advantages of MXene flakes and MoS2 nanosheets through
the hydrothermal method. In such a design, the well-dispersed MXene
flakes can effectively reduce the aggregation of MoS2 nanosheets,
boost electrical conductivity, and provide efficient charge transfer
paths. Furthermore, MoS2 nanosheets as the high-capacity
interlayer spacer can prevent the self-restacking of MXene flakes
and provide more active sites for ion intercalation. Meanwhile, the
strong chemical interactions between MXene flakes and MoS2 nanosheets contribute to accelerating the charge transfer kinetics
and enhancing structural stability. Consequently, the resulting MoS2@MXene heterostructure electrode possesses high specific capacitance
(171.4 F g–1), fast charge transfer and permeation
rate, abundant Na+ diffusion channels, and superior electrochemical
stability. Moreover, the hybrid CDI cell (AC//MoS2@MXene)
with AC as the anode and MoS2@MXene as the cathode delivers
outstanding desalination capacity (35.6 mg g–1),
rapid desalination rate (2.6 mg g–1 min–1), excellent charge efficiency (90.2%), and good cyclic stability
(96% retention rate). Most importantly, the MoS2@MXene
electrode can keep good structural integrity after the long-term repeated
desalination process due to the effective shielding effect of the
MoS2 layer to protect MXenes from being further oxidized.
This work presents the flexible structural engineering to realize
excellent ion transfer and storage process by constructing the 3D
heterostructure.