Polyethylene assisted CNTs in-situ growth on Fe-Mn-O to boost the electrochemical and electrocatalytic performance

Efficient reuse of plastic wastes is turning waste into treasure, and crucial to green and sustainable development. Herein, a flexible strategy was proposed to fabricate the composite of transition metal and carbon nanotubes (CNTs), i.e., polyethylene (PE) assisted CNTs in-situ growth on Fe-Mn-O. Mn-O and Fe-Mn-O was sequentially prepared via the coprecipitation method and impregnation method, and used for CNTs synthesis from PE via the thermo-catalytic process. It was found that PE facilitated CNTs in-situ growth on Fe-Mn-O, and CNTs yield was 456.1 mg/g, which was mostly in a hollow cylindrical structure with a heterogenous metal-particle. Based on the metal yarmulke structure, the in-situ growth of CNTs on Fe-Mn-O seemed to follow the tip growth mode. Compared with Fe-Mn-O, the in-situ growth of CNTs significantly improved the electrochemical and electrocatalytic performance. Fe-Mn-O/CNTs composite exhibited a specific capacitance of 135 F/g at 0.3 A/g in 1 M Na₂SO₄ electrolyte solution and an oxygen evolution reaction (OER) overpotential of 306 mV at 50 mA/cm² in 1 M KOH electrolyte solution, which was 75 F/g higher and 59 mV lower than that of Fe-Mn-O (60 F/g and 365 mV), respectively. It was deduced that the in-situ growth of CNTs effectively reduced the electrochemical impedance and improved the charge transport, and thus promoted the electrochemical and electrocatalytic performance of Fe-Mn-based materials. This work may provide a new direction for the resource of plastic wastes and the preparation of advanced transition metal/CNTs composites in the energy conversion and storage application.