Amorphous Thin-Walled Carbon Nanotubes Modified by Simple Oxidation for Zinc-Ion Hybrid Supercapacitors

Carbon nanotubes (CNTs) with superior one-dimensional dynamic properties are good cathode materials for zinc-ion hybrid supercapacitors (ZHSs). Meanwhile, surface oxidation is a productive strategy to boost electrochemical properties of CNTs. Compared with the conventional modification by the mixed strong acid (H₂SO₄/HNO₃), herein, a strategy is proposed to modify the thin-walled carbon nanotubes (TCNTs) through the oxidation of H₂O₂. The abundant −OH of TCNTs-H₂O₂ can enhance the hydrophilicity of TCNTs and the adsorption ability of Zn²⁺. Moreover, the electrochemical performance of ZHSs is obviously improved due to the synergistic effect between the bilayer capacitance of TCNTs and the pseudocapacitance of oxygen functional groups. Consequently, the assembled ZHSs exhibit excellent energy densities (80 Wh kg^-1 at 80 W kg^-1) and satisfactory long cycle stability (capacitance retention of 100% at 5 A g^-1 over 10,000 cycles). In general, TCNTs-H₂O₂ is a high-performance, very safe, and environmentally friendly electrode material for ZHSs.