Cobalt–iron decorated tellurium nanotubes for high energy density supercapacitor

Abstract

We report the synthesis of cobalt-iron (Co–Fe) decorated tellurium nanotubes (Te NTs) using semiconductive Te NTs as a sacrificial template, following a wet chemical method. The interplay of Co and Fe precursor concentrations incorporated with Te NT, residual hydrazine hydrate, and the negative surface charge of Te NT plays a significant role in obtaining various bimetallic telluride structures. The one-dimensional (1-D) structure of Co–Fe decorated Te NTs with Te NTs in the backbone provides superior conductivity and exhibits high electrochemical performance with battery type electrode behavior. A negative surface charge value of −18.9 mV for Te NTs is obtained due to the presence of an anionic surfactant as sodium dodecyl sulfate (SDS) forms a bilayer on Te NTs. To tune the energy density performance, the Co–Fe decorated Te NTs electrode is combined with the electric double-layer capacitors (EDLC) type electrode activated carbon (AC). The asymmetric assembly shows an excellent specific capacitance of 179.2 F/g (48.7 mAh/g) at a current density of 0.9 A/g in 4 M KOH electrolyte. More importantly, it exhibits a maximum energy density of 62.1 Wh/kg at a power density of 1,138.2 W/kg under a potential window of 1.58 V. This potential finding shows the significant applicability of Te NTs as a template for the synthesis of bimetallic tellurides with unique morphologies. The synergistic effect from multiple metals and anisotropic morphology is beneficial for energy storage applications.