Highly uniform deposition of MoO₃ nanodots on multiwalled carbon nanotubes for improved performance of supercapacitors

We demonstrate the sonochemical synthesis of multiwalled carbon nanotubes (MWCNTs) and MoO₃ hybrids for an application in supercapacitor (SC) electrodes. The MoO₃ nanodots with the diameter of <10 nm are uniformly deposited on the surfaces of MWCNTs as characterized by TEM and STEM images. The specific capacitance of 103 F g^-1 in MoO ₃/MWCNT hybrids is two times higher than 42 F g^-1 of the pristine MWCNTs and four times higher than 22 F g^-1 of MoO ₃. Moreover, hybrid electrodes show a good rate capability of >90% retention up to 2.12 A g^-1 and cyclic stability of 80% retention during 1000 cycles of charge/discharge because of the mechanical stability of the MWCNTs and the good contact between the MoO₃ and MWCNTs. The energy density of MoO₃/MWCNT hybrids is evaluated to be 38.7 Wh kg^-1 by using an organic electrolyte. Therefore, the hybridization of MWCNTs and redox-active MoO₃ nanodots provides a rational design strategy to overcome the critical challenges of pseudocapacitors such as poor rate and cycle stability, while improving the low specific capacitance of electric double layer capacitors (EDLCs).