Engineered nanoparticles (NPs) are vital to continued innovations in the battery industry. One common NP used in electric batteries is lithium cobalt oxide (LiCoO₂). Although widely popular, there remains little recycling infrastructure for LiCoO₂; therefore, it is deposited in landfills where it can leach into waterways and interact with the environment. Previous work has shown that LiCoO₂ undergoes transformations in aqueous environments. A byproduct of these transformations is the production of reactive oxygen species (ROS). ROS are fast-reacting molecules that are commonly produced in biological systems for cellular communication; however, in excess, these species become toxic to organisms. The nature and timescale of LiCoO₂ transformations, as well as the quantity and identity of ROS produced, are not well understood. Therefore, this work tracks LiCoO₂ transformations by detecting the ROS hydrogen peroxide (H₂O₂) generated from LiCoO₂ in water using amperometry over 26-hour time scales. To probe a range of spatial and temporal resolutions, experiments were conducted using a platinum-coated carbon-fiber microelectrode (PtCFME). PtCFMEs were shown to have a limit of detection near 10 mM H₂O₂. We present the ability to dynamically track LiCoO₂ transformations within a bulk solution. Studies on changes in the LCO surface chemistry before and after aqueous solution exposure are noted. The methodologies presented in this work can be applied to better understand the environmental impacts of a wide range of metal oxide NPs, thereby providing insight on long-term NP toxicity mechanisms and NP transformations.

David Ajayi

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