Comprehensive characterization of octahedral Co3O4 doped with Cu induces oxygen vacancies as a battery-type redox active electrode material for supercapacitors

The urgent need to combat global warming has spurred the exploration of renewable energy solutions, among which the supercapacitor has emerged as a promising contender for efficient energy storage in crucial applications. While battery-type electrode materials (BTMs), notably Co3O4, have shown impressive electrochemical performance in recent years, their inherent limitations, such as low conductivity, restricted surface area, and suboptimal electrochemical activity, pose challenges to their utility. Doping has emerged as a strategic solution to address these issues by modifying the crystal structure, surface morphology, specific surface area, electronic conductivity, and chemical stability of the host material, thereby enhancing its electrochemical performance. This study uses a combustion synthesis method to engineer octahedral Co3O4 with Cu-doping. We obtained three different samples of Co3O4: one undoped Co3O4, doped with 3 % Cu (3%Cu–Co3O4), and 6 % Cu (6%Cu–Co3O4). The addition of Cu not only changed the crystal structure and surface morphology but also impacted the surface area and defects (oxygen vacancies) in Co3O4, affecting its electrochemical performance. This doping method effectively controlled the oxygen vacancy defect content, as verified meticulously by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS). Particularly, the 6%Cu–Co3O4 configuration demonstrated significantly improved specific capacity (155.5 mA h g−1/559.8C g−1 at 1 A g−1) and rate performance (67 %), outperforming both 3%Cu–Co3O4 and undoped Co3O4. Additionally, it exhibited superior cycling stability with 91 % retention of the maximum specific capacity after 5000 cycles. Consequently, this study offers valuable insights into designing defect-engineered battery-type electrode materials for hybrid supercapacitors, which could significantly enrich their efficiency.