Non-Chemical Route to PGM-Free via N+ Ion Implantation in Vertically Aligned Carbon Nanotubes

Abstract

The continuous research on electrocatalytic nanomaterials for critical raw materials replacement has returned the important class of Platinum-group-metal-free electrocatalysts (PGM-free), based on C, N, and non-noble transition metals. PGM-free are employed in Fuel Cells, Zinc-Air batteries, and Electrolyzers to catalyze important energy-related reactions. They are usually synthesized following a chemical route based on mixing, pyrolyzing, and postprocessing of specific N- and transition metal-containing compounds into conductive C structures, leading to a high content of byproducts. Herein, for the first time, a new approach for PGM-free synthesis is investigated, based on nitrogen implantation via ion beam produced with a Kaufman apparatus, and iron evaporation inside a clean chamber. The performed investigation, based on a model sp² carbonaceous material (vertically aligned carbon nanotubes), showed similarities to the chemical route in terms of surface functionalization with the possibility to maximize the pyridinic N content, paving the way for the first time to the synthesis of nitrogen-compound-free nanoelectrocatalysts.