Post-consumer plastics/CoxMn3-xO4 spinels derived Co/MnO@carbon nanotube composites towards advanced electromagnetic absorbents

Waste plastics and electromagnetic radiation pollution have been two serious issues that largely affect our environment. How to solve them in a single approach is a social and scientific challenge. In this work, advanced Co/MnO@carbon nanotube composite (Co/MnO@CNTs) absorbents were prepared via pyrolysis-catalysis conversion of face masks as post-consumer plastic waste with multi-scale designed CoxMn3-xO4 spinel pre-catalysts. The (nano)structure (e.g., MnO-carbon and Co-carbon hetero-interface), composition, and graphitic degree of the Co/MnO@CNTs absorbents were facilely controlled by varying the catalytic reaction temperature and the composition of spinel pre-catalysts. By constructing multi-loss mechanisms (e.g., magnetic loss, conductive loss, interface polarization loss, and defects-induced polarization loss), the largest effective absorption bandwidth (EAB) of the Co/MnO@CNTs/wax composites can reach as wide as 5.28 GHz at a thickness of 1.7 mm. When the content of the Co/MnO@CNTs absorbents is 17 wt%, the EAB and minimal reflection loss (RLmin) achieves 5.04 GHz and -38.1 dB, respectively. This work is based on a sustainable and cost-effective feedstock as well as an innovative method for the large-scale production of advanced CNTs-based materials in electromagnetic absorption application.