Regulating NiMnO morphology to fine-tune CNTs growth from plastic wastes for engineering MnNiO/CNTs composite and energy storage

Abstract

Carbon nanotubes (CNTs) synthesis from plastic wastes is turning wastes into treasures and alleviating the environmental crisis. Herein, Mn-based supports were prepared by tailoring the crystallization temperature, and used for the fabrication of NiMnO nanoparticles via the impregnation method and 10 % Ni-loading. As increasing crystallization temperature from 120 °C to 150 °C further to 180 °C, the morphology of NiMnO nanoparticles evolved from irregular nanospheres (NM120) to uniform nanorods (NM150) further to nanosphere and nanorod mixture (NM180), and the assemble state evolved from irregular lump to honeycomb-like lump with uniform Ni, Mn and O distribution. Furthermore, NiMnO nanoparticles were used to regulate CNTs growth from polyethylene (PE). CNTs yield was in an order of NM180 (398.2 mg/g) > NM150 (217.9 mg/g) > NM120 (72.1 mg/g) with excellent graphitization degree and purity, which was mostly in the bamboo-like shape and metal-yarmulke structure. CNTs in-situ growth promoted the electrical conductivity of NiMnO/CNTs composite; while, the excessive CNTs reduced Mn-content, and was negative to the energy storage. Thus, the highest specific capacitance of 176 F/g at 0.3 A/g was obtained by NM150/CNTs composite. It was concluded that the synergistic effect of CNTs and Mn-based materials optimized the performance in the energy storage application.