Ni3S4 combined hydrophilic hydroxylated MWCNTs for high performance asymmetric supercapacitors

A composite material (Ni3S4-Q) of Ni3S4 combined with hydrophilic hydroxylated multi-walled carbon nanotubes (MWCNTs) was prepared by one-step method in the reactor. For comparison, hydrophilic MWCNTs were replaced by hydrophobic MWCNTs (Ni3S4-S), and pure Ni3S4 was synthesized without adding MWCNTs, so as to study the influence of the hydrophilicity and hydrophobicity of MWCNTs on the capacitive performance of Ni3S4. The contact Angle analysis shows that Ni3S4-Q has better hydrophilicity. The electrochemical cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy show that Ni3S4-Q has the highest specific capacitance and the lowest ion diffusion resistance. In addition, the asymmetric supercapacitor assembled by Ni3S4-Q and activated carbon has a maximum energy density of 51 Wh kg−1. This work strongly validated that hydrophilicity can improve the electrochemical properties of supercapacitors.