Preparation of Iron- and Nitrogen-Codoped Carbon Nanotubes from Waste Plastics Pyrolysis for the Oxygen Reduction Reaction

A novel method for the preparation of iron- and nitrogen-codoped carbon nanotubes (Fe-N-CNTs) is proposed, based on the catalytic pyrolysis of waste plastics. First, carbon nanotubes are produced from pyrolysis of plastic waste over Fe-Al2O3; then, Fe-CNTs and melamine are heated together in an inert atmosphere. Different co-pyrolysis temperatures are tested to optimize the electrocatalyst production. A high doping temperature improves the degree of graphite formation and promotes the conversion of nitrogen into a more stable form. Compared with commercial Pt/C, the electrocatalyst obtained from pyrolysis at 850 °C shows remarkable properties, with an onset potential of 0.943 V versus RHE and a half-wave potential of 0.811 V versus RHE, and even better stability and anti-poisoning properties. In addition, zinc–air battery tests are performed, and the optimized catalyst exhibits a high maximum power density.