Upcycling ambient particulate matter pollutants into high-performance carbon nanomaterials for electrochemical energy storage and oxygen evolution catalysis

The atmospheric aerosol consisting of particulate matter (i.e., PM_2.5 and PM₁₀) contain a substantial amount of carbon. In this innovative study, we present an oxidative chemical process for harnessing advanced carbon nanomaterials (nanodiamonds and carbon nanotubes) from PM₁₀ samples. The obtained nanodiamonds (NDs) and carbon nanotubes (CNTs) were examined using various chemical and advanced analytical techniques, including high-resolution electron microscopy. The NDs were unagglomerated and consistently dispersed, containing both crystalline and amorphous carbon. Additionally, short rod like clustered carbon particles with hollow or cylindrical morphologies, as well as aggregates with hollow-structured multiwalled CNTs, were observed. The synthesized NDs were smaller than 5 nm and exhibited bright blue fluorescence with excitation dependence. Furthermore, the PM₁₀-derived NDs and CNTs showed potential as electrolytes for electrochemical energy storage systems and as promising catalysts for the oxygen evolution reaction when compared with standards. Reusing these air pollutants helps to create valuable resources that may be utilized in various applications, reducing environmental impact and supporting the principles of environmental stewardship and the circular economy.