Abstract Amorphous RuO 2· xH 2O was well coated on the benzenesulfonic functionalized multi-wall carbon nanotubes (f-MWCNTs) successfully via hydrothermal method. The decorated benzenesulfonic groups served as a bifunctional role both for solubilizing and dispersing MWCNTs into aqueous solution and for tethering Ru 3+ precursor to facilitate the following uniform chemical deposition of RuO 2· xH 2O. The electrochemical performance of RuO 2/f-MWCNTs and utilization of RuO 2· xH 2O were evidenced by cyclic voltammetry and galvanostatic charge/discharge tests. The specific capacitance of 1143 Fg −1 for RuO 2· xH 2O was obtained from RuO 2/f-MWCNTs with 32 wt.% RuO 2· xH 2O, which was much higher than that of just 798 Fg −1 for the RuO 2/p-MWCNTs. Even though the RuO 2· xH 2O loading increases to 45 wt.%, the utilization of RuO 2· xH 2O still possesses as high as 844.4 Fg −1, indicating a good energy capacity in the case of high loading.