Sustainable Capture and Conversion of Carbon Dioxide into Valuable Multiwalled Carbon Nanotubes Using Metal Scrap Materials

Increasing amounts of nondegradable waste and rising levels of atmospheric carbon dioxide (CO2) similarly threaten a sustainable future, leaving routes to address these issues at the forefront of ongoing research efforts. Here, we demonstrate a route where electrochemical processing of scrap metals extracts catalytic species to the surface that actively convert CO, scavenged from the atmosphere to form multiwalled carbon nanotubes (M-VVCNTs). Our findings demonstrate two distinct pathways for this technique that is generalizable to a broad range of scrap metals. First is the case where the catalytic elements are the primary constituents of the material (e.g., Fe in stainless steel) and the reaction with CO, consumes the material. Second is the case where the catalytic elements are impurities (e.g., Fe in brass) where reaction with CO, leads to impurity consumption. Our results demonstrate facile growth of MWCNTs directly from irregular scraps, such as shavings and pipes. Overall, this study presents a route where input sources of atmospheric CO, and low-value metal scraps can be transformed to higher valued purified metals and high valued MWCNTs with the promise of an overall carbon negative capture and conversion strategy.