Annealing effect on the performance of RuO2-Ta2O5/Ti electrodes for use in supercapacitors

The preparation of RuO2-Ta2O5/Ti electrodes, by dip-coating, for use in supercapacitors was investigated. The stability and specific capacitance of the electrodes annealed at various temperatures was examined. The results show that highly stable electrodes with a specific capacitance of 170 F g RuO2−1 were obtained at approximately 250 °C, while electrodes with a lower capacitance (130 F g RuO2−1) were obtained at 300 °C. The annealing time needed to obtain a stable RuO2-Ta2O5/Ti electrode at various temperatures correlates well with the Arrhenius' law: with the activation energy (E) of the annealing reactions for the electrodes being estimated as 73.5 kJ mol−1. SEM images of the electrodes show the coating films to have rough surface morphology with cracks 2-6 μm in width. XRD data indicate that the coating films obtained are composed of crystalline RuO2 and amorphous tantalum oxide.