Study On Ruthenium Oxides/Carbon Nanotube Electrodes For Electrochemical Supercapacitors

Due to high energy density and power density in comparing with conventional capacitors and battery, electrochemical capacitors (ECs) have been received more and more attentions in peak-power source for electric vehicles, backup-power storage for calculators and starting power for fuel cells. In order to obtain practical capacitors, excellent capacitive properties of electrodes are required. Ruthenium oxides, because of their high specific capacitance, have been widely recognized as promising materials for ECs. However, due to high cost, their extensive applications are limited. On the other hand, carbon nanotubes (CNTs), with regard to their novel properties, nanometer size and high surface area, have been received an increasing attention in recent years for their applications in supercapacitors, but their specific capacitance is low. Combining each characteristic of ruthenium oxides and CNTs, we prepared a series of ruthenium oxides/CNTs composite electrodes and also investigated their electrochemical properties in H2SO4 aqueous solutions. The main results obtained in this paper are shown as follows:1. Three different electrodes were prepared using different methods: (a) RuO_x·H₂O/CNTs/graphite (G) composite electrode (Electrode â… ) prepared by deposition of ruthenium oxides on directly grown CNTs using cyclic voltammetry, (b) RuO₂·xH₂O/CNTs/G composite electrode (Electrode â…¡) prepared by "pulse deposition-CVD growth-electrochemical oxidation" route, and (c) RuO_x·nH₂O/ACNTs/G composite electrode (Electrode â…¢) prepared by deposition of ruthenium oxides on directly grown aligned carbon nanotubes array (ACNT) using cyclic voltammetry.2. SEM and TEM investigation show that all of the electrodes have three dimensional structures with uniform ruthenium oxides dispersion. Moreover, for RUO₂·xH₂O/CNTs/G electrode (Electrode â…¡), ruthenium oxides exist not only on the surface but also in the inner of the electrode. The morphology of RuO_x·nH₂O/ACNTs/G electrode (Electrode â…¢) has a unique directional three dimensional structures which is different from that of RuO_x·nH₂O/CNTs/G electrode.3. Electrochemical properties of three electrodes investigated in 0.5M H₂SO₄ aqueous solutions indicate that all electrodes exhibit pseudo capacitive behavior. For...