Recycling and valorization of LDPE: direct transformation into highly ordered doped-carbon materials and their application as electro-catalysts for the oxygen reduction reaction

Abstract

The energy demand and the environmental situation make the development of advanced catalysts for energy applications necessary. Considering the large volumes of plastic waste, the transformation of organic polymers into advanced carbon functional materials that are able to accomplish the oxygen reduction reaction via the desired 4-electron pathway is proposed as an integrated environmental remediation, in which plastic pollutants are converted into catalysts for fuel cells. Carbon-based electro-catalysts were obtained by pyrolyzing low-density polyethylene at low temperature by an easy one-step method that involves the generation of autogenous pressure which is the responsible for the spherical shape as well as the high degree of graphitization. The addition of transition metals (Fe, Co or Ni) modifies the carbonization process and CNFs emerge. The metal-free material leads to a purely 2e⁻ pathway; however, the presence of metals improves all electrochemical parameters and the desired 4e⁻pathway is achieved. The graphitization degree, the metal dispersion and the presence of CNFs are the key factors for the ORR performance.