Reverse-engineered borohydride hydrolysis: Vacancy-rich cobalt aerogel nanowafers as high-efficiency electrode materials for supercapacitor applications

Transition metal oxide aerogels (AGLs) have garnered considerable attention over the past decade due to their unique and exceptional properties, including high porosity, extensive surface area, and ultra-low density. To meet the rising energy requirements and the need for renewable energy storage solutions, there is a growing demand for devices offering high energy and power densities. To realize such a device, a reverse borohydride hydrolysis method was employed in this study to synthesize oxygen vacancy-rich cobalt-based AGL (CoAGL) nanowafers with Co2+/Co3+ defect chemistry. Additionally, we annealed CoAGL samples at 400 °C (CoAGL@400) to successfully design and fabricate three-electrode supercapacitors. The characterization techniques encompassed X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron studies, shedding light on the X-ray properties of these AGLs. CoAGL demonstrated a specific capacitance (Csp) of 42.3 F/g in a device setup, displaying excellent cyclability and capacitance retention. Furthermore, it exhibited an energy density of 14.4 Wh/kg and a power density of 800 W/kg at a current density of 1 A/g, respectively. The practical application of the aerogel was demonstrated by fabricating a two-electrode device employing CoAGL as the key component.