Ruthenium oxide thin film electrodes for supercapacitors

A ruthenium oxide thin film electrode with an average specific capacitance of 650 F/g and good high rate capability was prepared by electrostatic spray deposition (ESD). This technique is a one-step process of preparing ruthenium oxide thin film electrode compared with a multistep sol-gel process and has features of low-temperature synthesis and easy control of surface morphology. While as-prepared hydrous ruthenium oxide (RuO₂·xH₂O) thin film was in an amorphous phase, the hydrous ruthenium oxide (RuO₂·xH₂O) thin film became crystalline after annealing at temperatures >200°C. Ruthenium oxide thin film electrode annealed at 200°C showed a cyclic voltammogram indicative of a typical capacitive behavior in 0.5 M H₂SO₄ electrolyte at a scan rate of 20 mV/s with the average specific capacitance of 650 F/g. The average specific capacitance was 640 F/g at 2 mV/s and 600 F/g at 50 mV/s, respectively, indicating that the average specific capacitance decreases only slightly with increasing scan rate.