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.