Synergistic effect of CuCo2O4 and self-doped TiO2 nanotubes in binder-free electrodes for high-performance supercapacitors

Abstract

In this work, a high-performance binder-free electrode for supercapacitor applications is fabricated using self-doped TiO₂ nanotube arrays (TNAs) adorned with copper cobaltite (CuCo₂O₄). A two-step electrochemical anodization technique was used to produce highly ordered TNAs with a large surface area and electrochemical properties. To improve electrical conductivity, oxygen vacancies, and Ti³⁺ states were added to the pristine TNAs during the self-doping process. Instead of requiring polymer binders, these nanotube arrays act as a strong scaffold. Following that, an easy electrochemical deposition procedure was used to uniformly deposit CuCo₂O₄ nanoparticles onto the self-doped TNAs. Due to its large surface area, superior electron transport capabilities, and numerous redox-active sites, the resulting self-doped TNA/CuCo₂O₄ composite greatly improves electrochemical performance. A significant capacitive behavior was observed when the electrodes were examined in Na₂SO₄ electrolyte. Measurements using cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) revealed a long cycle stability, good rate capability, and high areal capacitance. The self-doped TNA electrode achieves the greatest areal capacitance of 29.19 mF/cm² at a current density of 0.1 mA/cm², along with good rate capability and long-term cycle stability, with capacitance retention of 97.36% after 5000 cycles. A remarkable areal capacitance of 669.59mF/cm² was achieved for the self-doped TNAs/CuCo₂O₄ electrode at a scan rate of 5 mV/s. The synergistic impact of self-doped TiO₂ and CuCo₂O₄ in increasing electron transfer and ion diffusion was further confirmed by electrochemical impedance spectroscopy (EIS), which also indicated a low charge-transfer resistance (R_ct) of 4.641 Ω. Combining the benefits of pseudocapacitive characteristics of CuCo₂O₄ with the improved conductivity of self-doped TNA, the self-doped TNA/CuCo₂O₄ composite electrode presents a potential option for energy storage devices. This binder-free, self-doped TNA electrode decorated with CuCo₂O₄ shows great promise for application in the next generation of supercapacitors, providing enhanced cycling durability, power density, and energy density.