Synergy of Lithium, Cobalt, and Oxygen Vacancies in Lithium Cobalt Oxide for Airborne Benzene Oxidation: A Concept of Reusing Electronic Wastes for Air Pollutant Removal

In this study, a recovery strategy of turning cathode materials of waste lithium-ion batteries, lithium cobalt oxide (LiCoO2), into high-performance catalysts for the oxidation of airborne benzene is investigated. Part of the Co3+ in LiCoO2 was leached out from the [CoO6] octahedra by HNO3 solution via the disproportion reaction with the deintercalation of interlayer Li+ ions, resulting in the formations of Li, Co, and O vacancies. The presence of Li and O vacancies facilitated gaseous benzene adsorption and subsequent activation of adsorbed benzene, and the Co vacancies together with the oxygen vacancies induced the generation of plenty of active surface oxygen species, accordingly the catalytic activity of the acid-modified LiCoO2 was greatly improved with good resistance to the alternative “heating-cooling” operation and stability from 0.8 to 2.3 vol % of humidity. More importantly, the acid modification process is green since the HNO3 solution could be reused many times to produce effective catalysts, and the final solution containing high concentrations of Li+ and Co2+ ions could be potentially recycled for cathode material manufacturing. The acid treatment method also worked effectively with the commercial LiCoO2. This study would inspire the development of novel and sustainable catalytic systems for environmental applications.