Synthesis and utilization of RuO2·xH2O nanodots well dispersed on poly(sodium 4-styrene sulfonate) functionalized multi-walled carbon nanotubes for supercapacitors

Abstract

RuO₂·xH₂O nanodots highly dispersed onto the surfaces of poly(sodium 4-styrene sulfonate) (PSS) functionalized multi-walled carbon nanotubes (FMWCNTs) were successfully synthesized via a polymer-assisted technique under mild hydrothermal conditions. Here, PSS served as a bifunctional molecule both for solubilizing and dispersing MWCNTs into aqueous solution and for tethering Ru³⁺ to facilitate the subsequent uniform formation of RuO₂·xH₂O nanodots on their surfaces. The dependence of electrochemical utilization of RuO₂·xH₂O nanodots on their dispersity was evidenced by cyclic voltammetry results. The maximum specific capacitance of 1474 F g⁻¹ and electrochemical utilization of 71% for the Ru species were obtained from RuO₂·xH₂O/FMWCNTs nanocomposite with 10 wt% RuO₂·xH₂O. And even for the 45 wt% RuO₂·xH₂O loading, the utilization of 34% still could be delivered, much higher than that of just 23% for the bare RuO₂·xH₂O nanodots. Such good supercapacitive performance of the nanocomposites should result from the high dispersity of the electroactive RuO₂·xH₂O nanodots on the FMWCNTs, resulting in the abundant electroactive surface atoms contacted by the H⁺ ions through the three-dimensional mesoporous conducting matrix easily even in the case of the high loadings of ruthenium oxide.