One-pot synthesis of core/shell Co@C spheres by catalytic carbonization of mixed plastics and their application in the photo-degradation of Congo red

Much attention has been paid to the synthesis of core/shell metal@carbon composites, but many of the proposed methods are limited by sophisticated procedure and expensive precursors. Herein, a facile one-pot approach is established to prepare magnetic core/shell Co@C spheres through catalytic carbonization of mixed plastics (consisting of polypropylene, polyethylene and polystyrene) by Co3O4 at 700 degrees C. The yield, composition, morphology, phase structure, textural property, surface element composition, thermal stability and magnetic property of core/shell Co@C spheres are investigated. The core/shell Co@C spheres have a distinct ordered and curved graphitic structure, and their main diameters are in the range of 110-130 nm. Besides, they show a ferromagnetic behavior with high saturation magnetization (85.6-101.6 emu g(-1)). Furthermore, it was observed that Co3O4 was uniformly distributed in mixed plastics and formed a network structure, which provided a precondition for the carbonization of mixed plastics into core/shell Co@C spheres with uniform sizes. Finally, the core/shell Co@C spheres were found to show high performance in photo-degradation of Congo red (CR) with good recyclablity, reusability and long-term stability. It was demonstrated that the outer carbon shell promoted the degradation of CR and served as a protective layer for cobalt core to improve acid resistance, while the inner cobalt core accelerated the decomposition of H2O2 into radicals, which catalyzed the degradation of CR. More importantly, this simple approach offers a potential way to prepare magnetic core/shell metal@carbon composites from cheap waste plastics.