A pH-Tailored Anodic Deposition of Hydrous RuO₂ for Supercapacitors

A pH-tailored anodic deposition strategy is reported in this work, by which the hydrous ruthenium oxide (RuO₂) can be directly deposited on titanium (Ti) substrates. The prepared RuO₂ electrode exhibits a well kinetic performance (the remarkably low equivalent series resistance of R_es∼2 mΩ and charge transfer resistance of R_ct∼0.11Ω) and a high specific capacitance of 756 F g^-1 at 0.6 A g^-1. More importantly, a symmetric supercapacitor based on the RuO₂ electrode delivers a high specific energy of 24 Wh kg^-1 at 150 W kg^-1. Even at a large specific power of 26.25 kW kg^-1, specific energy is still as high as 8.6 Wh kg^-1, meanwhile achieving a long lifespan of 98% retention over 100,000 cycles. All of these distinguishing properties not only enable the prepared RuO₂ to be an excellent electrode material for high-power output and long life supercapacitors, but also indicates that the pH-tailored anodic deposition strategy reported in this work is effective to prepare high-performance RuO₂ electrode.