Novel acid-free process intensification for the synthesis of non-precious metal-nitrogen-carbon electrocatalysts for oxygen reduction reaction

In this work, a set of PGM-free mono-metallic electrocatalysts (FeAD-N-CAF, Co-N-CAF, Mn-N-CAF, Ni-N-CAF) were synthesized using multiple silica templates with a modified acid-free sacrificial support method, characterized and tested for oxygen reduction reaction (ORR) in acidic, neutral and alkaline electrolytes. The removal of the silica template is achieved simultaneously to pyrolysis through the addition of Teflon powder to the mass of precursors before the heat treatment, resulting in a simple, fast and green approach compared to the conventional method based on the use of hydrofluoric acid (HF). Rotating ring disk electrode tests show that the iron-based electrocatalyst, among all, have higher activity for ORR. An electrocatalyst loading study was conducted with FeAD-N-CAF revealing a dual-site reaction mechanism and a maximum activity reached at 700 μg cm-2, while accelerated durability test highlights its promising stability. This novel synthesis route can be classified as a new intensified sustainable synthesis process.