Self-assembled RuO₂ nanoneedles on Ta/Cu foil for a robust and high-performance supercapacitor electrode

High-density self-assembled RuO₂ nanoneedles (NNs) are successfully fabricated on a tantalum (Ta)-coated copper (Cu) substrate via a mild hydrothermal reaction for an electrochemical supercapacitor electrode with a superior energy storage capacity and excellent electrochemical stability. The electrochemical properties of the RuO₂ NNs based electrode in a diluted H₂SO₄ electrolyte are investigated. The extremely thin Ta insertion layer enhances the adhesion between the RuO₂ NNs and the copper foil charge collector, thereby significantly enhancing the mechanical and electrochemical energy storage characteristics of the RuO₂ NNs electrode. The proposed electrode exhibits a remarkable capacitive storage performance of 1420 F g⁻¹ at a scan rate of 5 mV s⁻¹ and excellent long-term cycling stability (∼ 98% of capacitance is retained at 100 mV s⁻¹ after several hundred cycles). Moreover, the electrode shows a high energy density of ∼ 13 Wh kg⁻¹ at a power density of 27 kW kg⁻¹. The proposed strategy can facilitate the design of binder-free robust nanostructured oxide/hydroxide electrodes and can be extended to prepare high-performance catalysts and battery anodes.