In the work, amorphous CoSx nanodots were highly dispersed onto poly(sodium-4-styrene sulfonate) (PSS) functionalized multi-walled carbon nanotubes (FMWCNTs) by a interface-hydrothermal method. Electrochemical data demonstrated a specific capacitance (SC) of 300 F g(-1) was delivered at 3 A g(-1) by the nanocomposite, which was 90% of that at 0.4 A g(-1), indicating its good rate response. The good dispersion of the electroactive CoSx nanodots onto the FMWCNTs should be responsible for its better supercapacitive performance. Such unique structure made the abundant electroactive surface atoms of the CoSx phase contacted by OH- ions and electrons easily through the three-dimensional mesoporous conducting matrix of FMWCNTs for fast energy storage. Furthermore, the SC retention of ca. 95% reveals a good electrochemical stability of the nanocomposite. Crown Copyright (C) 2010 Published by Elsevier Inc. All rights reserved.