Fabrication of Fe–Zr, Co–Zr, and Ni–Zr Catalysts to Boost CNTs Synthesis from Plastic Wastes and the Electrocatalytic Oxygen Evolution Reaction

Abstract

The efficient conversion of plastic wastes to highvalue carbon materials like carbon nanotubes (CNTs) is one important issue about the rational recycling, reduction, and reuse of solid wastes. Herein, Fe−, Co−, and Ni−Zr catalysts were prepared and used for CNTs synthesis from polyethylene (PE) waste via a two-stage reaction system. At the same time, the effects of the PE/catalyst ratio and reaction temperature on CNTs synthesis have been studied. Compared with Co−Zr and Ni−Zr, Fe−Zr exhibited the best activity in CNTs synthesis from PE, and it achieved the highest CNTs yield of 806.3 mg/g (per gram of Fe−Zr) at 800 °C with a PE/catalyst ratio of 4. Furthermore, the obtained Fe−Zr/CNTs composite exhibited a low overpotential of 267 mV for the electrocatalytic oxygen evolution reaction (OER) at 20 mA/cm 2 in 1 M KOH electrolyte solution, which was 21 mV lower than commercial RuO 2 (288 mV) and 50 mV lower than Fe−Zr (317 mV). It was deduced that the in situ growth of CNTs reduced the charge transfer resistance and improved the electron transport efficiency of the Fe−Zr/CNTs composite, leading to superior activity in the electrocatalytic OER. This work provided detailed information for the preparation of the metal/CNTs composite from plastic wastes, which contributed positively to alleviate the environment and energy crisis.