One-Step Microwave-Assisted Synthesis of Metal-Free Heteroatom-Doped Carbon Catalyst for H2o2 Electrosynthesis

Abstract

This study reports on a one-step conversion of polyaniline into a metal-free heteroatom-doped carbon electrocatalyst through microwave heating. A high surface area carbonaceous structure forms just after a total synthesis time of 140 s, with the presence of nitrogen and oxygen functional groups, as confirmed by thorough spectroscopic analysis. This catalyst exhibits high activity (onset potential of 0.73 V vs. RHE), selectivity (82%), and stability (7.5 h) for the electrochemical oxygen reduction reaction towards hydrogen peroxide in alkaline media. Microwave synthesis reduces heating time by 29-fold and energy consumption by 77-fold, while producing materials with high electrocatalytic efficiency comparable to those conventionally prepared at 700 °C. The microwave and the conventionally synthesized heteroatom-doped carbon catalysts show similar electrochemical performances, which can be attributed to the presence of nearly identical nitrogen functional groups and surface area in the two samples. In contrast, the microwave and conventionally synthesized samples exhibit significant variations in their oxygen functional groups. These results suggest that nitrogen functional groups are the main active sites for alkaline hydrogen peroxide formation, while oxygen functional groups play a minor role in the catalytic activity. Our work brings a solid contribution to the debate regarding the active centers for hydrogen peroxide formation.

Keywords: microwave-assisted synthesis, heteroatom-doped carbon, hydrogen peroxide electrosynthesis, Oxygen reduction reaction, spectroscopy analysis