High-Purity V2O5 Nanosheets Synthesized from Gasification Waste: Flexible Energy Storage Devices and Environmental Assessment

Gasification waste, also known as carbon soot, is solid industrial waste from the bottom residual of an oil refinery and contains a substantial amount of toxic vanadium. In this work, we report an environmentally responsible pathway to harvest toxic vanadium from gasification waste, and the extracted vanadium can be utilized to synthesize high-purity V2O5 nanosheets for the fabrication of flexible, bendable, efficient supercapacitors. The carbonaceous waste was first rinsed with alkaline solution to leach out toxic vanadium. The vanadium-rich leachate was next utilized to synthesize high-quality V2O5 crystals with comparable purity (>98%) and crystallinity to commercial products. Two-dimensional V2O5 nanosheets were further crystallized by hydrothermal treatment for the fabrication of high-performance electrochemical electrodes. The V2O5 electrodes derived from gasification waste demonstrated similar specific capacitance (172 F g–1) to those from commercial V2O5 (173 F g–1). The waste-derived V2O5 nanosheets were further mixed with leached carbon nanoparticles for the fabrication of a symmetric, bendable, and flexible supercapacitor. The waste-derived V2O5 supercapacitor was able to be bent up to 160° and retained its specific capacitance. An environmental impact assessment was finally conducted to evaluate the environmental impacts of producing V2O5 crystals from gasification waste (in terms of the damage to human health, ecosystem diversity, and resource availability). The waste-derived approach was compared with traditional mining processes and showed a large improvement in all three endpoint damage categories.