High performance tellurium-reduced graphene oxide pseudocapacitor electrodes

Abstract

We report on facile preparation of Tellurium (Te)-reduced graphene oxide (rGO) electrodes for evaluation of electrochemical parameters. Initially, Te (0.5–11w/w %) was, in-situ, incorporated while reduction of graphene oxide. In material analysis, 1% Te optimised C/O ratio by rearrangement of C(O)O, separating oxygen from graphene plane, and self-oxidation. TeO bridging acted as an ideal strain buffer that modified nature of conjugation, folding, and exfoliated rGO sheets advantageous for pseudo-capacitive action. Electrochemical analysis, showed substantial increase in specific capacitance, Csp(@5 mV/s), for 1% Te-rGO, to 460 F/g from base rGO (270 F/g) with increase in charge-discharge time (CD@0.5A/g) 15 (rGO) to 100 s (Te-rGO). For two electrodes, CV (285 F/g @ 5 mV/s) and CD (260 F/g @0.25A/g) data was in well agreement with greatest CD ∼ 250 s for (1%). The CD time was retarded by a factor of six in both electrode studies, at 1%. The estimated energy, ED(Wh/kg), and power density, PD (W/kg), indicated that, both electrodes were at the interface of battery and electrode double layer capacitor (EDLC) region on Ragone plane. However, 1%Te-rGO at low PD(250) and high ED (8) have battery-like behaviour, whereas, at high PD (1002) and low ED(5) showed pseudo-capacitive action. Investigations on Nyquist, ac complex capacitance (Bode), and phase plots quantified contribution of impedances offered by surface, interface (electrolyte/active electrode/collector), charge transfer, and ions. Te-rGO showed excellent cycle stability 100% even after 2500 cycles @ 1A/g. By and large, 1% Te showed superior pseudo capacitive performance compared over high Te % and base rGO.