Rechargeable carbonaceous geosupercapacitor for sustainable superoxide generation and pollutant abatement

Reactive oxygen species enable efficient oxidative removal or detoxification of pollutants in water but traditional approaches for reactive oxygen species generation are chemically demanding, which limits their practical applications. Herein, we demonstrate a sustainable and chemical-free superoxide (O₂^•−) generation strategy by integrating rechargeable carbonaceous supercapacitors with redox-moiety-based O₂ activation, which is distinct from production using traditional electrocatalysis. Highly porous carbonaceous geosupercapacitors were developed by pyrolysing cattle bones consisting of macromolecules interlinked with abundant minerals, followed by acid etching. Porous geosupercapacitors exhibit high capacitances and excellent electron-transfer efficiencies for O₂ activation as a result of their abundant carbon defects and redox-active quinone moieties, thereby effectively transferring electrons to O₂ to form O₂^•− radicals. Electrochemical analysis shows that the electron-transfer rate of the carbonaceous geosupercapacitor is orders of magnitude higher than that of traditional biochar, notably promoting electron transfer and O₂ activation. This geosupercapacitor possesses excellent electron rechargeability and a stable capacitance, enabling sustainable O₂^•− production off-line. The utility of this green O₂^•− producing system is confirmed in different scenarios, such as stable performance in complex matrices, treating diverse redox-active pollutants and development of a portable chargeable device.