Hydrogen-Bonded Chemical Energy Storage Mechanism of Ruthenium Oxide-Coated Porous Silicon Nanowires

Aqueous ammonium ion-based (NH₄ ⁺) hybrid supercapacitors (AAHSCs) are attracting great attention because of their excellent electrochemical performance and environmental friendliness. Silicon nanowires have attracted extensive attention due to their unique physical/chemical properties that make them appealing in emerging energy conversion and storage applications. In this work, porous silicon nanowires (p-SiNWs) were used as scaffolds to coat RuO₂ nanospheres by hydrothermal treatment. The as-prepared RuO₂ nanospheres completely encapsulate the silicon nanowires, providing abundant active sites for NH₄ ⁺ attachment. The O-atoms in RuO₂ combine with NH₄ ⁺ to form hydrogen bonds (H-bonds), which greatly improve the electrochemical performance by promoting the charges transport through H-bonds formation/breaking during charging/discharging. In comparison with pure p-SiNWs, RuO₂@p-SiNWs electrode exhibits a higher areal capacitance of 128 mF/cm² at 0.1 mA. The capacitor is prepared with RuO₂@p-SiNWs as the cathode and activated carbon (AC) as the anode, separated by (NH₄)₂SO₄ electrolyte, achieving an aerial capacitance of 35.9 mF/cm² at the current of 0.2 mA. The proposed concept opens new avenue for developing advanced high-energy-density cathode materials for AAHSCs.